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#include <cstdio>
#include <algorithm>
#include "maklib.h"
#include "message.h"

using namespace std;

int n;
int nodes;
int myId;
int left, right;
long long total, smallest, result, totalBefore, smallestBefore;

int ceil(int p, int q)
{
	if(p % q == 0)
		return p/q;
	return p/q + 1;
}

void getLeft()
{
	left = ceil(n, nodes) * myId + 1;
}

void getRight()
{
	right =  min(ceil(n,nodes) * (myId + 1), n);
}

void getTotal()
{
	total = 0;
	totalBefore = 0;
	for(int i = left;i<=right;i++)
		total += ElementAt(i);
	if(myId != 0)
	{
		Receive(myId - 1);
		totalBefore = GetLL(myId - 1);
		total += totalBefore;
	}
	if(myId != nodes - 1)
	{
		PutLL(myId + 1, total);
		Send(myId + 1);
	}
}

void getSmallest()
{
	smallest = 0;
	long long temp = totalBefore;
	for(int i = left;i<=right;i++)
	{
		temp += ElementAt(i);
		smallest = min(temp, smallest);
	}
	if(myId != 0)
	{
		Receive(myId - 1);
		smallestBefore = GetLL(myId - 1);
		smallest = min(smallest, smallestBefore);
	}
	if(myId != nodes - 1)
	{
		PutLL(myId + 1, smallest);
		Send(myId + 1);
	}
}

void getResult()
{
	result = 0;
	smallest = smallestBefore;
	long long temp = totalBefore;
	for(int i = left;i<=right;i++)
	{
		temp += ElementAt(i);
		smallest = min(temp, smallest);
		result = max(result, temp - smallest);
	}
	if(myId != 0)
	{
		Receive(myId - 1);
		result = max(result, GetLL(myId - 1));
	}	
	if(myId != nodes - 1)
	{
		PutLL(myId + 1, result);
		Send(myId + 1);
	}
}

int main() 
{
	nodes = NumberOfNodes();
	myId = MyNodeId();
	n = Size();
	getLeft();
	getRight();
	getTotal();
	getSmallest();
	getResult();
	if(myId == nodes - 1)
		printf("%lld\n", result);
	return 0;
}