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#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,n) for (auto i = (a), i ## __ = (n); i <= i ## __; ++i)
#define FORD(i,a,n) for (auto i = (a), i ## __ = (n); i >= i ## __; --i)
#define REP(i,n) FOR(i, 0, n - 1)
#define REPD(i, n) FORD(i, n - 1, 0)
#define ALL(x) x.begin(), x.end()
#define SZ(x) (int(x.size()))
#define EB emplace_back
#define V vector
#define ST first
#define ND second
#define RS resize

template<class T, class B> inline void mini(T &&a, B &&b) { if (b < a) a = b; }
template<class T, class B> inline void maxi(T &&a, B &&b) { if (b > a) a = b; }
int ceil2(int x) { return x < 2 ? 1 : 1 << (sizeof(x) * 8 - __builtin_clz(x - 1)); }

constexpr char nl = '\n';
template<class T> struct DumpOff { T a, b; };
template<class T> auto dumpOff(T &x) -> DumpOff<decltype(x.begin())> { return {x.begin(), x.end()}; }
template<class T> auto dumpOff(T &x) -> decltype(cerr << x, x) { return x; }
template<class T> auto dumpOff(T &x) -> decltype(x.first, x) { return x; }
struct Debug {
    ~Debug() { cerr << nl; }
    template<class T> auto operator<<(T x) -> decltype(cerr << x, *this) { cerr << dumpOff(x); return *this; }
    template<class T> auto operator<<(T x) -> decltype(x.begin(), *this) {
        cerr << "{\n";
        for (auto a = x.begin(), b = x.end(); a != b; ++a)
            *this << "  " << distance(x.begin(), a) << ": " << dumpOff(*a) << '\n';
        return *this << "}";
    }
    template<class T, class B> Debug& operator<<(pair<T, B> p) { return *this << "(" << dumpOff(p.first) << ", " << dumpOff(p.second) << ")"; }
    template<class T> Debug& operator<<(DumpOff<T> d) {
        cerr << "{";
        for (auto a = d.a, b = d.b; a != b; ++a)
            *this << dumpOff(*a) << (next(a) == b ? "" : ", ");
        return *this << "}";
    }
};
struct Foo {template<class T>Foo& operator<<(T) {return *this;}};
 
#ifdef DEBUG
# define D Debug()
#else
# define D Foo()
# include "message.h"
# include "kanapka.h"
#endif
#define I(x...) #x ": " << x << "   "
 
typedef long long LL;
typedef pair<int, int> PII;
typedef V<int> VI;
typedef V<VI> VVI;
typedef V<PII> VPII;
typedef V<VPII> VVPII;
typedef V<bool> VB;
typedef V<VB> VVB;
typedef V<LL> VLL;


int main()
{
    LL n = GetN();
    int NON = NumberOfNodes();
    LL ID = MyNodeId();

    if(LL(NON) > n) NON = n;
    if(ID >= NON)
        return 0;

    int k = n / (NON);
    int r = n - (NON) * k;
    int a = k * (ID);
    int b = k * (ID + 1) - 1;
    if(ID < r) a += ID, b += ID + 1;
    else a += r, b += r;

    VLL front(b - a + 1);
    VLL back(b - a + 1);

    LL sfr = 0, sba = 0;

    int q = 0;
    FOR(i, a, b)
    {
        sfr += GetTaste(i);
        front[q] = sfr;
        if(q != 0) maxi(front[q], front[q - 1]);
        q++;
    }

    q = b - a;
    FORD(i, b, a)
    {
        sba += GetTaste(i);
        back[q] = sba;
        if(q != b - a) maxi(back[q], back[q + 1]);
        q--;
    }

    LL pref = 0, suff = 0;
    LL mxfr = 0, mxba = 0;

    if(ID != 0) 
    {
        Receive(ID - 1);
        pref = GetLL(ID - 1);
        mxfr = GetLL(ID - 1);
    }

    if(ID != NON - 1)
    {
        PutLL(ID + 1, sfr + pref);
        PutLL(ID + 1, max(mxfr, front[q - 1] + pref));
        Send(ID + 1);
        Receive(ID + 1);
        suff = GetLL(ID + 1);
        mxba = GetLL(ID + 1);
    }

    if(ID != 0)
    {
        PutLL(ID - 1, sba + suff);
        PutLL(ID - 1, max(mxba, back[0] + suff));
        Send(ID - 1);
    }

    LL mx = 0;
    maxi(mx, max(mxfr, pref) + max(mxba, suff + back[0]));
    REP(i, b - a)
        maxi(mx, max(mxfr, pref + front[i]) + max(mxba, suff + back[i + 1]));
    maxi(mx, max(mxfr, pref + front[b - a]) + max(mxba, suff));

    if(ID != 0) PutLL(0, mx), Send(0);
    else
    {
        REP(i, NON - 1)
            Receive(i + 1), maxi(mx, GetLL(i + 1));
        cout << mx << "\n";
    }

    return 0;
}