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#include "maklib.h"
#include "message.h"
#include <algorithm>
#include <iostream>
using namespace std;
//int NumberOfNodes() { return 1; }
//int Size() { return 10; }
//int MyNodeId() { return 0; }
//int ElementAt(int a) { cout << "ElementAt(" << a << ");\n"; return 5; }
//void Receive(int x) {}
//long long GetLL(int x) { return -1; }
//void PutLL(int a, long long x) {}
//void Send(int x) {}
int main() {
    long long n = Size();
    int m = NumberOfNodes();
    int x = MyNodeId();
    int beg = 1+(n*x)/m, end = 1+(n*(x+1))/m;
    long long maxPref=0, maxAny=0, maxSuf=0, pref=0, suf=0, maxTemp=0, sum=0;
    for (int i=beg; i<end; i++) {
        int a = ElementAt(i);
        sum += a;
        pref += a;
        maxTemp += a;
        if (maxTemp < 0) maxTemp = 0;
        maxAny = max(maxAny, maxTemp);
        maxPref = max(pref, maxPref);
    }
    for (int i=end-1; i>=beg; i--) {
        suf += ElementAt(i);
        maxSuf = max(suf, maxSuf);
    }
    long long bestBef = 0;
    if (x > 0) {
        Receive(x-1);
        bestBef = GetLL(x-1);
    }
    if (x < m-1) {
        PutLL(x+1, max(bestBef+sum, maxSuf));
        Send(x+1);
    }
    long long best = max(maxAny, bestBef+maxPref);
    if (x > 0) {
        PutLL(0, best);
        Send(0);
    } else {
        long long res = best;
        for (int i=1; i<m; i++) {
            Receive(i);
            res = max(res, GetLL(i));
        }
        cout << res << endl;
    }
    return 0;
}