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#include <algorithm>
#include <cstdio>

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

typedef long long LL;
int main(){
	int numberOfNodes = NumberOfNodes();
	int myNodeId = MyNodeId();
	LL size = Size();
	int begin = (size * myNodeId) / numberOfNodes + 1;
	int end = (size * (myNodeId + 1)) / numberOfNodes + 1;
	LL maxInfixSum = 0;
	LL maxPrefixSum = 0;
	LL maxSuffixSum = 0;
	LL totalSum = 0;
	
	LL minPrefixSum = 0;
	for(int i = begin; i < end; i++)
	{
		totalSum += ElementAt(i);
		maxPrefixSum = std::max(maxPrefixSum, totalSum);
		minPrefixSum = std::min(minPrefixSum, totalSum);
		maxInfixSum = std::max(maxInfixSum, totalSum - minPrefixSum);
	}
	maxSuffixSum = totalSum - minPrefixSum;
	
	for (int i = 1; i <= numberOfNodes; i <<= 1){
		int other = myNodeId ^ i;
		if(other >= numberOfNodes)
			continue;
		if(myNodeId & i){
			PutLL(other, maxInfixSum);
			PutLL(other, maxPrefixSum);
			PutLL(other, maxSuffixSum);
			PutLL(other, totalSum);
			Send(other);
			return 0;
		} else {
			Receive(other);
			LL maxInfixSum2 = GetLL(other);
			LL maxPrefixSum2 = GetLL(other);
			LL maxSuffixSum2 = GetLL(other);
			LL totalSum2 = GetLL(other);
			maxInfixSum = std::max(maxInfixSum, std::max(maxInfixSum2, maxSuffixSum + maxPrefixSum2));
			maxPrefixSum = std::max(maxPrefixSum, totalSum + maxPrefixSum2);
			maxSuffixSum = std::max(maxSuffixSum2, maxSuffixSum + totalSum2);
			totalSum += totalSum2;
		}
	}
	printf("%lld\n", maxInfixSum);
}