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#include<cstdio>
#include<algorithm>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<cmath>
#include<iostream>
#include<string>
#include"message.h"
#include"kanapka.h"
using namespace std;
#define F first
#define S second
#define MP make_pair
#define PB push_back
#define LL long long
#define PII pair<int, int>
#define PLL pair<LL, LL>

LL n, res, x, y;
int nods, nodn;
int p, k;
vector<PLL> P;
LL a, b, c, d;//left, right, sum, best;

int main()
{
	//ios_base::sync_with_stdio(0);
	nodn=MyNodeId();
	nods=NumberOfNodes();
	n=GetN();
	if(n<nods)
	{
		if(nodn>0)
			return 0;
		for(int i=0; i<n; i++)
		{
			if(i>0)
				P.PB(MP(GetTaste(i), P[i-1].S));
			else
				P.PB(MP(GetTaste(i), 0));
			if(i>0)
				P[i].F+=P[i-1].F;
			P[i].S=max(P[i].F, P[i].S);
		}
		for(int i=n-1; i>=0; i--)
		{
			if(i>0)
				x+=P[i].F-P[i-1].F;
			else
				x+=P[i].F;
			res=max(res, y+P[i].S);
			y=max(y, x);
		}
		res=max(res, y);
		printf("%lld\n", res);
		return 0;
	}
	p=((n+nods-1)/nods)*nodn;
	k=min(p+((n+nods-1)/nods)-1, n-1);
	if(p>k)
	{
		PutLL(0, 0);
		Send(0);
		return 0;
	}
	for(int i=p; i<=k; i++)
	{
		if(i>p)
			P.PB(MP(GetTaste(i), P[i-p-1].S));
		else
			P.PB(MP(GetTaste(i), 0));
		if(i>p)
				P[i-p].F+=P[i-p-1].F;
		P[i-p].S=max(P[i-p].F, P[i-p].S);
	}
	for(int i=k; i>=p; i--)
	{
		if(i>p)
			x+=P[i-p].F-P[i-p-1].F;
		else
			x+=P[i-p].F;
		y=max(y, x);
	}
	if(nodn==0)
	{
		PutLL(1, P[k-p].F);
		PutLL(1, P[k-p].S);
		Send(1);
	}
	else
	{
		Receive(nodn-1);
		a=GetLL(nodn-1);
		b=GetLL(nodn-1);
		if(k<n)
		{
			PutLL(nodn+1, a+P[k-p].F);
			PutLL(nodn+1, max(b, a+P[k-p].S));
			Send(nodn+1);
		}
	}
	if(k==n)
	{
		PutLL(nodn-1, P[k-p].F);
		PutLL(nodn-1, y);
		Send(nodn-1);
	}
	else
	{
		Receive(nodn+1);
		c=GetLL(nodn+1);
		d=GetLL(nodn+1);
		if(nodn>0)
		{
			PutLL(nodn-1, c+P[k-p].F);
			PutLL(nodn-1, max(d, c+y));
			Send(nodn-1);
		}
	}
	x=c;
	y=d;
	for(int i=k; i>=p; i--)
	{
		if(i>p)
			x+=P[i-p].F-P[i-p-1].F;
		else
			x+=P[i-p].F;
		res=max(res, y+max(b, a+P[i-p].S));
		y=max(y, x);
	}
	res=max(res, y);
	if(nodn>0)
	{
		PutLL(0, res);
		Send(0);
	}
	else
	{
		for(int i=1; i<nods; i++)
		{
			Receive(i);
			res=max(res, GetLL(i));
		}
		printf("%lld\n", res);
	}
	return 0;
}