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#include "message.h"
#include "kanapka.h"
#include <cmath>
#include <iostream>
#include <vector>

using namespace std;

typedef long long ll;

// tablice sum ciagow lewostronnych i prawostronnych konczacych sie w danym indeksie
vector<ll> from_left;
vector<ll> from_right;
// sumy najkorzystniejszych ciagow lewostronnych i prawostronnych
ll best_left_sum, best_right_sum;

void count_table(ll s, ll e, ll* sum) {
	*sum = 0;
	ll current;

	from_left.resize(e - s);
	from_right.resize(e - s);

	for (ll i = s; i < e; i++) {
		current = GetTaste(i);
		from_left[i - s] = *sum + current;
		*sum += current;
	}
	*sum = 0;
	for (ll i = e - 1; i >= s; i--) {
		current = GetTaste(i);
		from_right[i - s] = *sum + current;
		*sum += current;
	}
}

ll update_table(ll s, ll e, ll left_sum, ll right_sum) {
	ll best = 0;
	best_left_sum = best_right_sum = 0;
	for (ll i = 0; i < e - s; i++) {
		from_left[i] += left_sum;
		from_right[i] += right_sum;
		if (from_left[i] > best_left_sum) {
			best_left_sum = from_left[i];
		}
		if (from_right[i] > best_right_sum) {
			best_right_sum = from_right[i];
		}
	}

	ll fragments = (ll) pow(e-s,2.0/3.0);
	ll width = (ll) (e - s) / fragments;

	vector<ll> best_lefts(fragments);
	vector<ll> best_rights(fragments);
	vector<ll> bests(fragments);

	for (ll fragment = 0; fragment < fragments - 1; fragment++) {
		bests[fragment] = best_lefts[fragment] = best_rights[fragment] = 0;
		for (ll i = fragment * width; i < (fragment + 1) * width; i++) {
			if (from_left[i] > bests[fragment]) {
				bests[fragment] = from_left[i];
			}
			if (from_right[i] > bests[fragment]) {
				bests[fragment] = from_right[i];
			}
			if (from_left[i] > best_lefts[fragment]) {
				best_lefts[fragment] = from_left[i];
			}
			if (from_right[i] > best_rights[fragment]) {
				best_rights[fragment] = from_right[i];
			}
			for (ll gap = 1; i + gap < (fragment + 1) * width; gap++) {
				if (from_left[i] + from_right[i + gap] > bests[fragment]) {
					bests[fragment] = from_left[i] + from_right[i + gap];
				}
			}
		}
	}
	bests[fragments - 1] = best_lefts[fragments - 1] =
			best_rights[fragments - 1] = 0;
	for (ll i = (fragments - 1) * width; i < e - s; i++) {
		if (from_left[i] > bests[fragments - 1]) {
			bests[fragments - 1] = from_left[i];
		}
		if (from_right[i] > bests[fragments - 1]) {
			bests[fragments - 1] = from_right[i];
		}
		if (from_left[i] > best_lefts[fragments - 1]) {
			best_lefts[fragments - 1] = from_left[i];
		}
		if (from_right[i] > best_lefts[fragments - 1]) {
			best_rights[fragments - 1] = from_right[i];
		}
		for (ll gap = 1; i + gap < e - s; gap++) {
			if (from_left[i] + from_right[i + gap] > bests[fragments - 1]) {
				bests[fragments - 1] = from_left[i] + from_right[i + gap];
			}
		}
	}

	for (ll i = 0; i < fragments; i++) {
		if (bests[i] > best)
			best = bests[i];
	}

	for (ll gap = 1; gap < fragments; gap++) {
		for (ll i = 0; i + gap < fragments; i++) {
			if (best_lefts[i] + best_rights[i + gap] > best) {
				best = best_lefts[i] + best_rights[i + gap];
			}
		}
	}
	best_lefts.clear();
	best_rights.clear();
	bests.clear();
	from_left.clear();
	from_right.clear();
	return best;
}

int main() {
	ll s, e; // zakres mojego wezla
	ll sum; // suma elementow w moim wezle
	ll left_sum, right_sum; // suma wszystkich elementow na lewo ode mnie i na prawo ode mnie (beze mnie)
	ll active_nodes = NumberOfNodes() > GetN() ? GetN() : NumberOfNodes();

	if (active_nodes == GetN()) {
		s = MyNodeId();
		e = MyNodeId() + 1;
	} else {
		s = MyNodeId() * (GetN() / NumberOfNodes());
		if (MyNodeId() == NumberOfNodes() - 1) {
			e = GetN();
		} else {
			e = (MyNodeId() + 1) * (GetN() / NumberOfNodes());
		}
	}

	if (MyNodeId() < active_nodes) {
		// obliczam tablice najdluzszych podciagow z lewej i z prawej strony
		count_table(s, e, &sum);

		if (active_nodes > 1) {
			// wymiana sum lewych miedzy wezlami
			if (MyNodeId() == 0) {
				left_sum = 0;
				PutLL(MyNodeId() + 1, sum);
				Send(MyNodeId() + 1);
			} else {
				Receive(MyNodeId() - 1);
				left_sum = GetLL(MyNodeId() - 1);
				if (MyNodeId() < active_nodes - 1) {
					PutLL(MyNodeId() + 1, left_sum + sum);
					Send(MyNodeId() + 1);
				}
			}

			// wymiana sum prawych
			if (MyNodeId() == active_nodes - 1) {
				right_sum = 0;
				PutLL(MyNodeId() - 1, sum);
				Send(MyNodeId() - 1);
			} else {
				Receive(MyNodeId() + 1);
				right_sum = GetLL(MyNodeId() + 1);
				if (MyNodeId() > 0) {
					PutLL(MyNodeId() - 1, right_sum + sum);
					Send(MyNodeId() - 1);
				}
			}
		} else {
			left_sum = right_sum = 0;
		}
		// aktualizuje tablice sum wedlug uzyskanych sum lewych i prawych
		// przy okazji zapisuje najkorzystniejsze ciagi lewe i prawe
		// i obliczam najkorzystniejsze ciagi konczace sie w danym wezle
		ll best = update_table(s, e, left_sum, right_sum);

		if (MyNodeId() > 0) {
			PutLL(0, best_left_sum);
			PutLL(0, best_right_sum);
			PutLL(0, best);
			Send(0);
		} else {
			// lacze wyniki ze wszystkich wezlow
			vector<ll>best_lefts(active_nodes);
			vector<ll>best_rights(active_nodes);
			vector<ll>bests(active_nodes);

			best_lefts[0] = best_left_sum;
			best_rights[0] = best_right_sum;
			bests[0] = best;

			for (ll i = 1; i < active_nodes; i++) {
				Receive(i);
				best_lefts[i] = GetLL(i);
				best_rights[i] = GetLL(i);
				bests[i] = GetLL(i);
			}

			ll the_best = 0;

			for (ll i = 0; i < active_nodes; i++) {
				if (bests[i] > the_best)
					the_best = bests[i];
			}

			for (ll gap = 1; gap < active_nodes; gap++) {
				for (ll i = 0; i + gap < active_nodes; i++) {
					if (best_lefts[i] + best_rights[i + gap] > the_best) {
						the_best = best_lefts[i] + best_rights[i + gap];
					}
				}
			}
			cout << the_best;

			best_lefts.clear();
			best_rights.clear();
			bests.clear();
		}
	}
	return 0;
}