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#include "message.h"
#include "maklib.h"
#include <vector>
#include <algorithm>
#include <iostream>

struct Data
{
	Data(long long _a = 0, long long _b = 0, long long _c = 0, long long _d = 0)
		: a(_a), b(_b), c(_c), d(_d)
	{}

	void send(int _target)
	{
		PutLL(0, d);
		PutLL(0, c);
		PutLL(0, b);
		PutLL(0, a);
		Send(0);
	}

	static Data receive(int _source)
	{
		int source = Receive(_source);
		return {
			GetLL(source),
			GetLL(source),
			GetLL(source),
			GetLL(source)
		};
	}

	// -----
	long long a, b, c, d;
};

int main()
{
	int numOfNodes = (NumberOfNodes() > Size() ? Size() : NumberOfNodes());
	if (MyNodeId() >= numOfNodes) {
		return 0;
	}
	int begin = Size() / numOfNodes * MyNodeId() + 1;
	int end = begin + Size() / numOfNodes - 1;
	end = (MyNodeId() == numOfNodes - 1 ? Size() : end);
	Data mypack;

	long long b = 0, c = 0, d = 0;
	for (int i = begin; i <= end; ++i) {
		// a
		mypack.a += ElementAt(i);
		// b
		b += ElementAt(end - i + begin);
		mypack.b = std::max(mypack.b, b);
		// c
		c += ElementAt(i);
		mypack.c = std::max(mypack.c, c);
		// d
		if (d > 0) {
			d += ElementAt(i);
		} else {
			d = ElementAt(i);
		}
		mypack.d = std::max(mypack.d, d);
	}

	if (MyNodeId() == 0) {
		std::vector<Data> intel(numOfNodes);
		for (int i = 1; i < numOfNodes; ++i) {
			intel[i] = Data::receive(i);
		}
		intel[0] = mypack;
		long long mmax  = 0, total = 0;
		for (int i = 0; i < numOfNodes; ++i) {
			mmax = std::max(intel[i].d, mmax);
			mmax = std::max(total + intel[i].c, mmax);
			if (total + intel[i].a < intel[i].b) {
				total = intel[i].b;
			} else {
				total += intel[i].a;
			}
			mmax = std::max(total, mmax);
		}
		std::cout << mmax << '\n';
	} else {
		mypack.send(0);
	}

	return 0;
}