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#include <vector>
#include <list>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <iostream>
#include <string>

#include "message.h"
#include "maklib.h"

#define FOR(i,a,b)  for(int i=(a);i<(b);++i)
#define FORD(i,a,b) for(int i=(a);i>=(b);--i)
#define REP(i,a)    FOR(i,0,a)
#define MP          make_pair
#define PB          push_back
#define ST          first
#define ND          second

using namespace std;

typedef vector<int>             VI;
typedef vector<VI>              VVI;
typedef pair<int, int>          PII;
typedef vector<PII>             VII;
typedef long long int           LL;
typedef unsigned long long int  ULL;


int ProcNum, ProcID;
int N;

int main() {
    ProcNum = NumberOfNodes();
    ProcID = MyNodeId();
    N = Size();

    int begIdx = int(((LL(ProcID)) * LL(N)) / ProcNum);
    int endIdx = int((LL(ProcID + 1) * LL(N)) / ProcNum);

    LL maxPref = 0, maxSuf = 0, sum = 0, bestSum = 0;
    LL w = 0;
    FOR (i, begIdx, endIdx) {
        int x = ElementAt(i+1);
        sum += x;
        maxPref = max(maxPref, sum);
        maxSuf = max(maxSuf, -sum);
        if (w > 0) {
            w += x;
        }
        else {
            w = x;
        }
        bestSum = max(bestSum, w);
    }
    maxSuf += sum;
//cerr << ProcID << ": " << sum << " " << bestSum << " " << maxPref << " " << maxSuf << "\n";

    if (ProcID != 0) {
        PutLL(0, sum);
        PutLL(0, maxPref);
        PutLL(0, maxSuf);
        PutLL(0, bestSum);
        Send(0);
    }
    else {
        LL res = bestSum;
        vector<LL> sums(ProcNum), maxPrefs(ProcNum), maxSufs(ProcNum);
        sums[0] = sum;
        maxPrefs[0] = maxPref;
        maxSufs[0] = maxSuf;

        REP (i, ProcNum-1) {
            int senderID = Receive(-1);
            sums[senderID] = GetLL(senderID);
            maxPrefs[senderID] = GetLL(senderID);
            maxSufs[senderID] = GetLL(senderID);
            res = max(res, GetLL(senderID));
        }

        FOR (i, 0, ProcNum) {
            FOR (j, i+1, ProcNum) {
                LL tmp = maxSufs[i] + maxPrefs[j];
                FOR (k, i+1, j) {
                    tmp += sums[k];
                }
                res = max(res, tmp);
            }
        }

        printf("%lld\n", res);
    }

    return 0;
}