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#include<algorithm>
#include<iostream>

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

int main()
{
	int number = NumberOfNodes();
	int id = MyNodeId();
	int size = Size();

	if(id >= size)
		return 0;
	if(number > size)
		number = size;

	int fragsize = size / number;
	int start = id * fragsize + 1;
	int end;
	if(id == number - 1)
		end = size;
	else
		end = (id + 1) * fragsize;

	long long tmp = 0;
	long long max = 0;
	long long sum = 0;
	long long pref = 0;
	for(int i = start; i <= end; ++i)
	{
		long long elem = ElementAt(i);
		tmp += elem;
		tmp = std::max(0LL, tmp);
		max = std::max(tmp, max);
		sum += elem;
		pref = std::max(sum, pref);
	}

	tmp = 0;
	long long suf = 0;
	for(int i = end; i >= start; --i)
	{
		tmp += ElementAt(i);
		suf = std::max(tmp, suf);
	}

	for(int iter = id, count = 0; (1 << count) < number; iter /= 2, ++count)
	{
		if(iter % 2 == 0)
		{
			int source = id + (1 << count);
			if(source >= number)
				continue;

			Receive(source);
			long long smax = GetLL(source);
			long long ssum = GetLL(source);
			long long spref = GetLL(source);
			long long ssuf = GetLL(source);

			max = std::max(max, std::max(smax, suf + spref));
			pref = std::max(pref, sum + spref);
			suf = std::max(ssuf, ssum + suf);
			sum += ssum;
		}
		else
		{
			int target = id - (1 << count);

			PutLL(target, max);
			PutLL(target, sum);
			PutLL(target, pref);
			PutLL(target, suf);
			Send(target);

			return 0;
		}
	}

	std::ios_base::sync_with_stdio(false);
	std::cout << max << std::endl;

	return 0;
}