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#include <algorithm>
#include <cstdio>
#include <utility>
#include <vector>

#include "kanapka.h"
#include "message.h"

int main_node;

int number_of_nodes;
int my_node;

long long int N;

std::vector<std::pair<long long int, long long int>> ranges;

void CollectAnswers() {
  long long int answer = 0ll;
  for (int i = 0; i < number_of_nodes; i++) {
    int from_whom = Receive(-1);
    answer = std::max(answer, GetLL(from_whom));
  }
  printf("%lld\n", answer);
}

void ComputeAnswer(long long int a, long long int b) {
  const int length = b - a + 1;
  Receive(main_node);
  long long int pref_sum = GetLL(main_node);
  long long int pref_max = GetLL(main_node);
  long long int suf_sum = GetLL(main_node);
  long long int suf_max = GetLL(main_node);
  std::vector<long long int> pref_maxes(length, 0ll);
  std::vector<long long int> suf_maxes(length, 0ll);
  for (int i = 0; i < length; i++) {
    pref_maxes[i] = pref_max = std::max(pref_max, pref_sum);
    pref_sum += GetTaste(a + i);
  }
  long long int answer = pref_sum + suf_sum;
  for (int i = length - 1; i >= 0; i--) {
    suf_maxes[i] = suf_max = std::max(suf_max, suf_sum);
    suf_sum += GetTaste(a + i);
  }
  for (int i = 0; i < length; i++) {
    answer = std::max(answer, pref_maxes[i] + suf_maxes[i]);
  }
  PutLL(main_node, answer);
  Send(main_node);
}

void CollectAccumulatedValues() {
  std::vector<long long int> sums(number_of_nodes);
  std::vector<long long int> pref_maxes(number_of_nodes);
  std::vector<long long int> suf_maxes(number_of_nodes);
  for (int i = 0; i < number_of_nodes; i++) {
    const int from_whom = Receive(-1);
    sums[from_whom] = GetLL(from_whom);
    pref_maxes[from_whom] = GetLL(from_whom);
    suf_maxes[from_whom] = GetLL(from_whom);
  }
  std::vector<std::pair<long long int, long long int>>
      first_part_of_message(number_of_nodes);
  long long int sum = 0ll;
  long long int pref_max = 0ll;
  long long int suf_max = 0ll;
  for (int i = 0; i < number_of_nodes; i++) {
    first_part_of_message[i].first = sum;
    first_part_of_message[i].second = pref_max;
    pref_max = std::max(pref_max, sum + pref_maxes[i]);
    sum += sums[i];
  }
  sum = 0ll;
  for (int i = number_of_nodes - 1; i >= 0; i--) {
    PutLL(i, first_part_of_message[i].first);
    PutLL(i, first_part_of_message[i].second);
    PutLL(i, sum);
    PutLL(i, suf_max);
    suf_max = std::max(suf_max, sum + suf_maxes[i]);
    sum += sums[i];
    Send(i);
  }
}

void AccumulateValues(long long int a, long long int b) {
  long long int sum = 0ll;
  long long int pref_max = 0ll;
  long long int suf_max = 0ll;
  for (long long int i = a; i <= b; i++) {
    sum += GetTaste(i);
    pref_max = std::max(pref_max, sum);
  }
  sum = 0ll;
  for (long long int i = b; i >= a; i--) {
    sum += GetTaste(i);
    suf_max = std::max(suf_max, sum);
  }
  PutLL(main_node, sum);
  PutLL(main_node, pref_max);
  PutLL(main_node, suf_max);
  Send(main_node);
}

void ComputeRanges() {
  long long int width = (N + number_of_nodes - 1) / number_of_nodes;
  int start_position = 0;
  for (int i = 0; i < number_of_nodes; i++) {
    int end_position = std::min(start_position + width, N);
    ranges.emplace_back(start_position, end_position - 1);
    start_position = end_position;
  }
}

int main() {
  main_node = number_of_nodes = NumberOfNodes() - 1;
  my_node = MyNodeId();
  N = GetN();
  ComputeRanges();
  if (my_node == main_node) {
    CollectAccumulatedValues();
  } else {
    AccumulateValues(ranges[my_node].first, ranges[my_node].second);
  }
  if (my_node == main_node) {
    CollectAnswers();
  } else {
    ComputeAnswer(ranges[my_node].first, ranges[my_node].second);
  }
  return 0;
}