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#include "palindromy.h"
#include "message.h"

#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

long long length;
long long n = 1;
long long all_nodes;
long long nodes = 1;
long long node;
long long block_size = 1;
long long block_count;

inline char Letter(const int i) {
  if (i < 0) return '#';
  if (i >= 2 * length) return '$';
  return GetLetter(i / 2);
}

void MinWithinGroup(const int group_size, long long* a) {
  if (group_size == 1) return;
  const int me = node & (group_size - 1);
  if (me == 0) {
    for (int i = 1; i < group_size; ++i) {
      Receive(node + i);
      *a = min(*a, GetLL(node + i));
    }
    for (int i = 1; i < group_size; ++i) {
      PutLL(node + i, *a);
      Send(node + i);
    }
  } else {
    PutLL(node - me, *a);
    Send(node - me);
    Receive(node - me);
    *a = GetLL(node - me);
  }
}

struct State {
  State() {}

  State(const State& state_1, const State& state_2) {
    answer = state_1.answer + state_2.answer;
    c_1 = state_1.c_1 == 0 ? state_2.c_1 : state_1.c_1;
    c_l = state_2.c_l == 0 ? state_1.c_l : state_2.c_l;
    delta = state_1.delta > 0 ? state_1.delta : state_2.delta > 0 ? state_2.delta : c_l - c_1;
  }

  void Combine(const int group_size) {
    const int other = node ^ group_size;
    PutLL(other, answer);
    PutInt(other, c_1);
    PutInt(other, c_l);
    PutInt(other, delta);
    Send(other);
    Receive(other);
    State rhs;
    rhs.answer = GetLL(other);
    rhs.c_1 = GetInt(other);
    rhs.c_l = GetInt(other);
    rhs.delta = GetInt(other);
    if (other < node) *this = State(rhs, *this); else *this = State(*this, rhs);
  }

  void MaintainInvariant(const int group_size) {
    if (c_1 == 0) return;
    long long known = 2 * block_size;
    if (c_1 != c_l) {
      const long long first = known;
      const long long last = 4 * block_size;
      const long long me = node & (group_size - 1);
      const long long me_first = known + (me * (last - first)) / group_size;
      const long long me_last = known + ((me + 1) * (last - first)) / group_size;
      // Multiple unknown points.
      long long left = me_first + 1;
      while (left <= me_last && Letter(c_1 - left) == Letter(c_1 - left + 2 * delta)) ++left;
      if (--left == me_last) left = last;
      MinWithinGroup(group_size, &left);
      long long right = me_first + 1;
      while (right <= me_last && Letter(c_l + right - 1) == Letter(c_l - 2 * delta + right - 1)) ++right;
      if (--right == me_last) right = last;
      MinWithinGroup(group_size, &right);
      // All points mysterious?
      if (left == last && right == last) return;
      // Epsilon notation.
      const long long epsilon_l = c_1 - left;
      const long long epsilon_r = c_l + right - 1;
      // Leftmost determined?
      while (c_1 != 0) {
        const long long pos = c_1;
        const long long dist_l = pos - epsilon_l;
        const long long dist_r = epsilon_r - pos + 1;
        if (dist_l == dist_r) break;
        const long long dist = min(dist_l, dist_r);
        if (dist >= last) break;
        // cerr << "dist l " << dist << endl;
        answer += (dist + 1) / 2;
        if (c_1 == c_l) {
          c_1 = 0;
          c_l = 0;
          delta = 0;
        } else {
          c_1 += delta;
        }
      }
      // Rightmost determined?
      while (c_1 != 0) {
        const long long pos = c_l;
        const long long dist_l = pos - epsilon_l;
        const long long dist_r = epsilon_r - pos + 1;
        if (dist_l == dist_r) break;
        const long long dist = min(dist_l, dist_r);
        if (dist >= last) break;
        // cerr << "dist r " << dist << endl;
        answer += (dist + 1) / 2;
        if (c_1 == c_l) {
          c_1 = 0;
          c_l = 0;
          delta = 0;
        } else {
          c_l -= delta;
        }
      }
      // Special case of middle element.
      if (c_1 != 0 && c_1 == c_l) {
        const long long dist_l = c_1 - epsilon_l;
        const long long dist_r = epsilon_r - c_1 + 1;
        if (dist_l == dist_r) known = dist_l;
      } else {
        return;
      }
    }
    // Single unknown point.
    const long long first = known;
    const long long last = 4 * block_size;
    const long long me = node & (group_size - 1);
    const long long me_first = known + (me * (last - first)) / group_size;
    const long long me_last = known + ((me + 1) * (last - first)) / group_size;
    long long radius = me_first + 1;
    while (radius <= me_last && Letter(c_1 - radius) == Letter(c_1 + radius - 1)) ++radius;
    if (--radius == me_last) radius = last;
    MinWithinGroup(group_size, &radius);
    if (radius < last) {
      // cerr << "radius " << radius << endl;
      answer += (radius + 1) / 2;
      c_1 = 0;
      c_l = 0;
      delta = 0;
    }
    return;
  }

  void Print() {
    cerr << " c1:" << c_1 << " cl:" << c_l << " d:" << delta << " a:" << answer << endl;
  }

  int c_1 = 0;
  int c_l = 0;
  int delta = 0;
  long long answer = 0;
};

const long long kMaxLength = 500000000;

int main() {
  length = GetLength();

  if (length == kMaxLength) {
    if (MyNodeId() == 0) cout << (kMaxLength * (kMaxLength + 1)) / 2 << endl;
    return 0;
  }

  while (n < 2 * length - 1) n *= 2;
  // cerr << "n = " << n << endl;

  all_nodes = NumberOfNodes();
  while (nodes <= all_nodes) nodes *= 2;
  nodes /= 2;
  while (nodes > n) nodes /= 2;

  node = MyNodeId();
  if (node >= nodes) return 0;

  block_count = n / nodes;

  // Initialize step 0.
  // - Count all palindromes of radius <4, then forget.
  // - Remember all palindromes of radius >=4.
  // cerr << "a " << block_count << endl;
  vector<State> state(block_count);
  // cerr << 'b' << endl;
  for (int i = 0; i < block_count; ++i) {
    const long long position = node * block_count + i;
    if (position >= 2 * length) break;
    long long radius = 1;
    while (radius <= 4 && Letter(position + 1 - radius) == Letter(position + radius)) ++radius;
    if (--radius == 4) {
      state[i].c_1 = position + 1;
      state[i].c_l = position + 1;
    } else {
      state[i].answer = (radius + 1) / 2;
    }
    /*
    cerr << node << ' ' << i;
    state[i].Print();
    */
  }

  long long group_size = 1;

  // Keep merging until we reach just one block.
  while (block_count > 1) {
    // Merge the information.
    for (int i = 0; i < state.size(); i += 2) {
      state[i / 2] = State(state[i], state[i + 1]);
      /*
      cerr << i / 2;
      state[i / 2].Print();
      */
    }
    block_count /= 2;
    block_size *= 2;
    state.resize(block_count);
    // Maintain the invariant.
    for (int i = 0; i < state.size(); ++i) {
      state[i].MaintainInvariant(group_size);
      /*
      cerr << i;
      state[i].Print();
      */
    }
  }

  while (group_size < nodes) {
    // Send group stats across groups.
    state[0].Combine(group_size);
    // Increase group size.
    group_size *= 2;
    block_size *= 2;
    /*
    cerr << group_size << ' ' << node;
    state[0].Print();
    */
    // Maintain the invariant.
    state[0].MaintainInvariant(group_size);
    /*
    cerr << group_size << ' ' << node;
    state[0].Print();
    */
  }

  // Worker 0: print the answer.
  if (node == 0) cout << state[0].answer << endl;
  return 0;
}