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#include "message.h"
#include "kanapka.h"

#include<climits>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<algorithm>
#include<vector>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<list>
#include<string>
#include<cstring>

using namespace std;

#define PB push_back
#define MP make_pair
#define F first
#define S second
#define ALL(x) (x).begin(),(x).end()
#define SIZE(x) (int)(x).size()
#define SORT(x) sort((x).begin(),(x).end())
#define CLEAR(tab) memset(tab, 0, sizeof(tab))
#define REP(x, n) for(int x = 0; x < (n); x++)
#define FOR(x, b, e) for(int x = (b); x <= (e); x++)
#define FORD(x, b, e) for(int x = (b); x >= (e); x--)
#define VAR(v, n) __typeof(n) v = (n)
#define FOREACH(i, c) for(VAR(i, (c).begin()); i != (c).end(); ++i)
#define DEBUG(fmt, ...) fprintf(stderr, fmt, ##__VA_ARGS__)

const int MAX_BUF_SIZE = 16384;
char BUFOR[MAX_BUF_SIZE];
int BUF_SIZE, BUF_POS;
char ZZZ;
#define GET(ZZZ){ZZZ='a';if(BUF_POS<BUF_SIZE)ZZZ=BUFOR[BUF_POS++];\
else if(!feof(stdin)){BUF_SIZE=fread(BUFOR,1,MAX_BUF_SIZE,stdin);\
ZZZ=BUFOR[0];BUF_POS=1;}}
#define GI(WW){do{GET(ZZZ);}while(!isdigit(ZZZ));WW=ZZZ-'0';\
while(1){GET(ZZZ);if(!isdigit(ZZZ))break;WW=WW*10+(ZZZ-'0');}}
#define GC(WW){do{GET(ZZZ);}while(!isalpha(ZZZ));WW=ZZZ;}

//FAST IO

typedef long long int LL;
typedef pair<LL,LL> PII;
typedef vector<LL> VI;

const int MXN = 1000010;
const int C = 262144;
const LL INF = LLONG_MAX;
const pair<PII, PII> kappa = MP(MP(INF, INF), MP(INF, INF) );

LL n;
VI a;

/* ( (pref, suf), (middle, sum) ) */
pair<PII, PII> solve(pair<int, int> x) {
	int pocz = x.F;
	int kon = x.S;

	if(pocz > kon)
		return MP(MP(INF, INF), MP(INF, INF) );
	LL mini, maksi;
	mini = maksi = GetTaste(pocz);
	LL sum = 0, mid = 0;
	LL tmp = 0;
	FOR(i, pocz, kon) {
		sum += GetTaste(i);
		mini = min(sum, mini);
		maksi = max(sum, maksi);
		if(tmp <= 0)
			tmp += GetTaste(i);
		else
			tmp = GetTaste(i);
		mid = min(mid, tmp);
	}

	return MP(MP(mini, sum - maksi), MP(mid, sum) );
}

LL solve2(vector< pair<PII, PII> > vec) {
	LL res = 0;
	LL totalSum = 0;
	FOREACH(it, vec)
		totalSum += (*it).S.S;
	FOREACH(it, vec)
		res = max(totalSum - (*it).S.F, res);
	
	int S = SIZE(vec);

	FOR(i, 0, S - 1)
		FOR(j, i + 1, S - 1) {
			LL tmp = vec[i].F.S + vec[j].F.F;
			FOR(o, i + 1, j - 1)
				tmp += vec[o].S.S;
				
			res = max(totalSum - tmp, res);
		}

	return res;
}

pair<int, int> getVec(int x) {
	int pocz = (x * n) / NumberOfNodes();
	int kon = ((x + 1) * n ) / NumberOfNodes();
	if(MyNodeId() == NumberOfNodes() - 1)
		kon = n;
	return MP(pocz, kon - 1);
}

void sendData(pair<PII, PII> tmp) {
	PutLL(0, tmp.F.F);
	PutLL(0, tmp.F.S);
	PutLL(0, tmp.S.F);
	PutLL(0, tmp.S.S);
	Send(0);
}

pair<PII, PII> getData(int id) {
	Receive(id);
	LL a1, a2, a3, a4;
	a1 = GetLL(id);
	a2 = GetLL(id);
	a3 = GetLL(id);
	a4 = GetLL(id);
	return MP(MP(a1, a2), MP(a3, a4) );
}

int main() {
	n = GetN();

	pair<PII, PII> tmp;
	tmp = solve(getVec(MyNodeId() ) );
	sendData(tmp);

	if(MyNodeId() == 0) {
		vector< pair<PII, PII> >vec;

		FOR(i, 0, NumberOfNodes() - 1) {
			pair<PII, PII> q = getData(i);
			if(q != kappa)
				vec.PB(q);
		}
		
		printf("%lld\n", solve2(vec) );
	}

	return 0;
}