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#ifndef LOCAL
#pragma GCC optimize ("O3")
#endif

#include <bits/stdc++.h>

#include "message.h"

using namespace std;

#define sim template < class c
#define ris return * this
#define dor > debug & operator <<
#define eni(x) sim > typename \
enable_if<sizeof dud<c>(0) x 1, debug&>::type operator<<(c i) {
sim > struct rge { c b, e; };
sim > rge<c> range(c i, c j) { return {i, j}; }
sim > auto dud(c* x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct debug {
#ifdef LOCAL
~debug() { cerr << endl; }
eni(!=) cerr << boolalpha << i; ris; }
eni(==) ris << range(begin(i), end(i)); }
sim, class b dor(pair < b, c > d) {
  ris << "(" << d.first << ", " << d.second << ")";
}
sim dor(rge<c> d) {
  *this << "[";
  for (c it = d.b; it != d.e; ++it)
    *this << ", " + 2 * (it == d.b) << *it;
  ris << "]";
}
#else
sim dor(const c&) { ris; }
#endif
};
#define imie(x...) " [" #x ": " << (x) << "] "

template <typename T>
typename make_signed<T>::type ToSigned(T t) {
  #pragma GCC diagnostic push
  #pragma GCC diagnostic ignored "-Wsign-compare"
  using ST = typename make_signed<T>::type;
  if (t <= numeric_limits<ST>::max()) {
    return static_cast<ST>(t);
  } else if (t >= numeric_limits<ST>::min()) {
    return static_cast<ST>(t - numeric_limits<ST>::min())
        + numeric_limits<ST>::min();
  } else {
    abort();
  }
  #pragma GCC diagnostic pop
}

using LengthType = uint32_t;

class SendMessage;

namespace SendMessageInternal {

template <typename T>
struct __Helper {
  static void Put(SendMessage& sm, const T& t);
};

#define SM_SIMPLE_TYPE(type)                            \
    template <>                                         \
    struct __Helper<type> {                             \
      static void Put(SendMessage& sm, const type& t);  \
    };

SM_SIMPLE_TYPE(bool);
SM_SIMPLE_TYPE(char);
SM_SIMPLE_TYPE(signed char);
SM_SIMPLE_TYPE(unsigned char);
SM_SIMPLE_TYPE(signed int);
SM_SIMPLE_TYPE(unsigned int);
SM_SIMPLE_TYPE(signed long);
SM_SIMPLE_TYPE(unsigned long);
SM_SIMPLE_TYPE(signed long long);
SM_SIMPLE_TYPE(unsigned long long);

#undef SM_SIMPLE_TYPE

template <typename A, typename B>
struct __Helper<pair<A, B>> {
  static void Put(SendMessage& sm, const pair<A, B>& p);
};

template <typename T>
struct __Helper<rge<T>> {
  static void Put(SendMessage& sm, const rge<T>& d);
};

}  // namespace SendMessageInternal

class SendMessage {
 private:
  int id_;
  bool is_sent_;

  static int nodes_;
  static int nodes();

  template <typename T>
  using CleanT = typename remove_reference<typename remove_cv<T>::type>::type;

 public:
  SendMessage(int target) : id_(target), is_sent_(false) {
    assert(0 <= id_ and id_ < nodes());
  }

  ~SendMessage() {
    if (!is_sent_) {
      Send();
    }
  }

  int id() const { return id_; }

  template <typename T>
  SendMessage& Put(const T& t) {
    SendMessageInternal::__Helper<CleanT<T>>::Put(*this, t);
    return *this;
  }

  void Send() {
    assert(!is_sent_);
    is_sent_ = true;
    ::Send(id_);
  }
};

int SendMessage::nodes_ = -1;
int SendMessage::nodes() {
  if (nodes_ == -1) nodes_ = NumberOfNodes();
  return nodes_;
}

namespace SendMessageInternal {

template <typename T>
void __PutResolver(SendMessage& sm, const T& t) {}

template <typename T, typename Ptr1, typename ...Ptrs>
void __PutResolver(SendMessage& sm, const T& t, Ptr1 ptr1, Ptrs ...ptrs) {
  sm.Put(t.*ptr1);
  __PutResolver(sm, t, ptrs...);
}

template <typename T>
void __Helper<T>::Put(SendMessage& sm, const T& t) {
  sm.Put(range(begin(t), end(t)));
}

#define SM_SIMPLE_TYPE(type, func1, func2)                      \
    void __Helper<type>::Put(SendMessage& sm, const type& t) {  \
      func2(sm.id(), func1(t));                                 \
    }

SM_SIMPLE_TYPE(bool, static_cast<char>, PutChar);
SM_SIMPLE_TYPE(char, , PutChar);
SM_SIMPLE_TYPE(signed char, , PutChar);
SM_SIMPLE_TYPE(unsigned char, , PutChar);
SM_SIMPLE_TYPE(signed int, , PutInt);
SM_SIMPLE_TYPE(unsigned int, ToSigned, PutInt);
SM_SIMPLE_TYPE(signed long, , PutLL);
SM_SIMPLE_TYPE(unsigned long, ToSigned, PutLL);
SM_SIMPLE_TYPE(signed long long, , PutLL);
SM_SIMPLE_TYPE(unsigned long long, ToSigned, PutLL);

#undef SM_SIMPLE_TYPE

template <typename A, typename B>
void __Helper<pair<A, B>>::Put(SendMessage& sm, const pair<A, B>& p) {
  sm.Put(p.first);
  sm.Put(p.second);
}

template <typename T>
void __Helper<rge<T>>::Put(SendMessage& sm, const rge<T>& d) {
  sm.Put(static_cast<LengthType>(distance(d.b, d.e)));
  for (T it = d.b; it != d.e; ++it) {
    sm.Put(*it);
  }
}

}  // namespace SendMessageInternal

class ReceiveMessage;

namespace ReceiveMessageInternal {

template <typename T>
struct __Helper {
  static T Get(ReceiveMessage& rm);
};

#define RM_SIMPLE_TYPE(type)                \
    template <>                             \
    struct __Helper<type> {                 \
      static type Get(ReceiveMessage& rm);  \
    }

RM_SIMPLE_TYPE(bool);
RM_SIMPLE_TYPE(char);
RM_SIMPLE_TYPE(signed char);
RM_SIMPLE_TYPE(unsigned char);
RM_SIMPLE_TYPE(signed int);
RM_SIMPLE_TYPE(unsigned int);
RM_SIMPLE_TYPE(signed long);
RM_SIMPLE_TYPE(unsigned long);
RM_SIMPLE_TYPE(signed long long);
RM_SIMPLE_TYPE(unsigned long long);

#undef RM_SIMPLE_TYPE

template <typename A, typename B>
struct __Helper<pair<A, B>> {
  static pair<A, B> Get(ReceiveMessage& rm);
};

}  // namespace ReceiveMessageInternal

class ReceiveMessage {
 private:
  int id_;

  static int nodes_;
  static int nodes();

  template <typename T>
  using CleanT = typename remove_reference<typename remove_cv<T>::type>::type;

 public:
  int id() const { return id_; }

  ReceiveMessage(int source) : id_(source) {
    assert(-1 <= id_ and id_ < nodes());
    id_ = Receive(id_);
    assert(0 <= id_ and id_ < nodes());
  }

  template <typename T>
  CleanT<T> Get() {
    return ReceiveMessageInternal::__Helper<CleanT<T>>::Get(*this);
  }
};

int ReceiveMessage::nodes_ = -1;
int ReceiveMessage::nodes() {
  if (nodes_ == -1) nodes_ = NumberOfNodes();
  return nodes_;
}

namespace ReceiveMessageInternal {

template <typename T>
void __GetResolver(ReceiveMessage& rm, T& t) {}

template <typename T, typename Ptr1, typename ...Ptrs>
void __GetResolver(ReceiveMessage& rm, T& t, Ptr1 ptr1, Ptrs ...ptrs) {
  t.*ptr1 = rm.Get<decltype(t.*ptr1)>();
  __GetResolver(rm, t, ptrs...);
}

template <typename T>
T __Helper<T>::Get(ReceiveMessage& rm) {
  T t;
  auto it = inserter(t, end(t));
  const LengthType len = rm.Get<LengthType>();
  for (LengthType i = 0; i < len; i++) {
    *it = rm.Get<typename T::value_type>();
  }
  return t;
}

#define RM_SIMPLE_TYPE(type, func1, func2)          \
    type __Helper<type>::Get(ReceiveMessage& rm) {  \
      return func1(func2(rm.id()));                 \
    }

RM_SIMPLE_TYPE(bool, static_cast<char>, GetChar);
RM_SIMPLE_TYPE(char, , GetChar);
RM_SIMPLE_TYPE(signed char, ToSigned, GetChar);
RM_SIMPLE_TYPE(unsigned char, , GetChar);
RM_SIMPLE_TYPE(signed int, , GetInt);
RM_SIMPLE_TYPE(unsigned int, , GetInt);
RM_SIMPLE_TYPE(signed long, , GetLL);
RM_SIMPLE_TYPE(unsigned long, , GetLL);
RM_SIMPLE_TYPE(signed long long, , GetLL);
RM_SIMPLE_TYPE(unsigned long long, , GetLL);

#undef RM_SIMPLE_TYPE

template <typename A, typename B>
pair<A, B> __Helper<pair<A, B>>::Get(ReceiveMessage& rm) {
  A a = rm.Get<A>();
  B b = rm.Get<B>();
  return {a, b};
}

}  // namespace ReceiveMessageInternal

#define REGISTER_MESSAGE(type, fields...)                  \
    namespace SendMessageInternal {                        \
      template <>                                          \
      struct __Helper<type> {                              \
        static void Put(SendMessage& sm, const type& d) {  \
          __PutResolver(sm, d, fields);                    \
        }                                                  \
      };                                                   \
    }                                                      \
    namespace ReceiveMessageInternal {                     \
      template <>                                          \
      struct __Helper<type> {                              \
        static type Get(ReceiveMessage& rm) {              \
          type t;                                          \
          __GetResolver(rm, t, fields);                    \
          return t;                                        \
        }                                                  \
      };                                                   \
    }

#define REGISTER_MESSAGE_CLASS(type, mclass)                 \
    namespace SendMessageInternal {                          \
      template <> struct __Helper<type> : public mclass {};  \
    }                                                        \
    namespace ReceiveMessageInternal {                       \
      template <> struct __Helper<type> : public mclass {};  \
    }

using ld = long double;
using ll = long long;

constexpr int mod = 1000 * 1000 * 1000 + 7;
constexpr int odw2 = (mod + 1) / 2;

void OdejmijOd(int& a, int b) { a -= b; if (a < 0) a += mod; }
int Odejmij(int a, int b) { OdejmijOd(a, b); return a; }
void DodajDo(int& a, int b) { a += b; if (a >= mod) a -= mod; }
int Dodaj(int a, int b) { DodajDo(a, b); return a; }
int Mnoz(int a, int b) { return (ll) a * b % mod; }
void MnozDo(int& a, int b) { a = Mnoz(a, b); }
int Pot(int a, int b) { int res = 1; while (b) { if (b % 2 == 1) MnozDo(res, a); a = Mnoz(a, a); b /= 2; } return res; }
int Odw(int a) { return Pot(a, mod - 2); }
void PodzielDo(int& a, int b) { MnozDo(a, Odw(b)); }
int Podziel(int a, int b) { return Mnoz(a, Odw(b)); }
int Moduluj(ll x) { x %= mod; if (x < 0) x += mod; return x; }

template <typename T> T Maxi(T& a, T b) { return a = max(a, b); }
template <typename T> T Mini(T& a, T b) { return a = min(a, b); }

template <typename T>
class Range {
 private:
  T a_, b_;

 public:
  Range() : Range(T(1), T(0)) {}
  Range(T a, T b) : a_(a), b_(b) {}

  Range GetPart(int i, int n) const {
    assert(0 <= i and i < n);
    const T len = length();
    const T part = len / n;
    const int ile_duzych = len % n;
    auto PartBeginning = [this, part, ile_duzych, n](int j) -> T {
      return a_ + j * part + min(ile_duzych, j);
    };
    return Range(PartBeginning(i), PartBeginning(i + 1) - 1);
  }

  vector<Range> Divide(int n) const {
    assert(0 < n);
    vector<Range> res(n);
    for (int i = 0; i < n; i++) {
      res[i] = GetPart(i, n);
    }
    return res;
  }

  T a() const { return a_; }
  T b() const { return b_; }
  bool empty() const { return a_ > b_; }
  const T length() const { if (empty()) return 0; else return b_ - a_ + 1; }

  Range& operator&=(const Range& r) {
    Maxi(a_, r.a_);
    Mini(b_, r.b_);
    return *this;
  }

  Range operator&(const Range& r) const {
    return Range(*this) &= r;
  }

  friend debug& operator<<(debug& deb, const Range& r) {
    if (r.empty()) return deb << "[empty]";
    else return deb << "[" << r.a() << ", " << r.b() << "]";
  }
};

template <typename T>
struct RangeMessageHelper {
  static void Put(SendMessage& sm, const Range<T>& r) {
    sm.Put(r.a()).Put(r.b());
  }

  static Range<T> Get(ReceiveMessage& rm) {
    const int a = rm.Get<int>();
    const int b = rm.Get<int>();
    return Range<T>(a, b);
  }
};

REGISTER_MESSAGE_CLASS(Range<int>, RangeMessageHelper<int>);
REGISTER_MESSAGE_CLASS(Range<ll>, RangeMessageHelper<ll>);

#include "teatr.h"

int N, me;

//REGISTER_MESSAGE(Data, &Data::a, &Data::b);

constexpr int nax = 1000 * 1000 + 105;
int zlicz[nax];
int pref[nax];
int suf[nax];

int drz[nax];
void Dodaj(int w) {
  while (w < nax) {
    drz[w]++;
    w += (w & (-w));
  }
}
int Sumuj(int w) {
  int res = 0;
  while (w > 0) {
    res += drz[w];
    w -= (w & (-w));
  }
  return res;
}

int main() {
  N = NumberOfNodes();
  me = MyNodeId();
  if (N % 2 == 0) {
    N--;
    assert(N >= 1);
  }
  if (me >= N) return 0;
  auto ranges = Range<int>(0, GetN() - 1).Divide(N);
  debug() << imie(N) imie(me) imie(ranges);
  vector<int> moje;
  for (int j = 0; j < N / 2; j++) {
    moje.push_back((me + 1 + j) % N);
  }
  vector<int> lewo, prawo;
  for (int x : moje) {
    assert(0 <= x and x < N);
    assert(x != me);
    if (x < me) lewo.push_back(x);
    else prawo.push_back(x);
  }
  debug() << imie(me) imie(lewo) imie(prawo);
  const ll len = ranges[me].length();
  ll wynik = (len * (len - 1)) / 2;
  for (int i = ranges[me].a(); i <= ranges[me].b(); i++) {
    const int e = GetElement(i);
    zlicz[e]++;
    wynik -= Sumuj(e);
    Dodaj(e);
  }
  for (int i = 1; i < nax; i++) {
    pref[i] = pref[i - 1] + zlicz[i];
  }
  for (int i = nax - 2; i >= 0; i--) {
    suf[i] = suf[i + 1] + zlicz[i];
  }
  for (int l : lewo) {
    for (int i = ranges[l].a(); i <= ranges[l].b(); i++) {
      wynik += pref[GetElement(i) - 1];
    }
  }
  for (int p : prawo) {
    for (int i = ranges[p].a(); i <= ranges[p].b(); i++) {
      wynik += suf[GetElement(i) + 1];
    }
  }
  debug() << imie(me) imie(wynik);
  if (me == 0) {
    for (int i = 1; i < N; i++) {
      wynik += ReceiveMessage(i).Get<ll>();
    }
    cout << wynik << endl;
  } else {
    SendMessage(0).Put(wynik);
  }
  return 0;
}