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

using namespace std;

typedef long long int64;

int element_at_getter (int i)
{
    return ElementAt(i);
}

static int64 * tab;

int64 array_getter (int i)
{
    return tab[i];
}

template <typename T_Elements>
tuple<int64, int64, int64, int64, int64> compute_max_subarray (T_Elements (*element_getter) (int), int begin, int end)
{

    int64 max_sum = 0, sum = 0, sum_from_begin = 0, sum_from_end = 0, sum_total = 0, sum_current, max_left = 0, max_right = 0;
    int b = -1, flag = 0;
    --end;

    for (int i = begin; i < end; ++i)
    {
        T_Elements x = element_getter(i);
        sum_total += x;
        max_left = max(max_left, sum_total);
        sum = max(sum + x, 0LL);
        if (sum > 0)
        {
            if (b == -1)
            {
                b = i;
                sum_current = sum_total - x;
                flag = 1;
            }
            if (sum > max_sum)
            {
                max_sum = sum;
                if (flag)
                {
                    sum_from_begin = sum_current;
                    flag = 0;
                }
            }
        }
        else
        {
            b = -1;
        }
    }

    // last iteration
    int i = end;
    if (i > 0)
    {
        T_Elements x = element_getter(i);
        sum_total += x;
        max_left = max(max_left, sum_total);
        sum = max(sum + x, 0LL);
        if (sum > 0)
        {
            if (b == -1)
            {
                b = i;
                sum_current = sum_total - x;
                flag = 1;
            }
            if (sum > max_sum)
            {
                max_sum = sum;
                if (flag)
                {
                    sum_from_begin = sum_current;
                    flag = 0;
                }
            }
            max_right = sum;
        }
        else
        {
            max_right = 0;
            b = -1;
        }
    }

    sum_from_end = (sum_total - sum_from_begin - max_sum);
    return make_tuple(max_sum, sum_from_begin, sum_from_end, max_left, max_right);
}

int main ()
{
    int size = Size();
    int nodes = NumberOfNodes();
    int me = MyNodeId();

    int start = (size / nodes) * me;
    int mod = (size % nodes);
    int end = (size / nodes) * (me + 1);

    if (me == nodes - 1)
    {
        end += mod;
    }

    tuple<int64, int64, int64, int64, int64> res = compute_max_subarray<int>(element_at_getter, start + 1, end + 1);

    if (me != 0)
    {
        PutLL(0, get<0>(res));
        PutLL(0, get<1>(res));
        PutLL(0, get<2>(res));
        PutLL(0, get<3>(res));
        PutLL(0, get<4>(res));
        Send(0);
    }
    else
    {
        tab = new int64 [nodes * 3];
        int64 leftright[nodes * 2];
        for (int i = 0; i < nodes - 1; i++)
        {
            int source = Receive(-1);
            int s_node = source;
            int64 s_sum = GetLL(source);
            int64 s_sfb = GetLL(source);
            int64 s_sfe = GetLL(source);
            int64 s_ml = GetLL(source);
            int64 s_mr = GetLL(source);

            tab[s_node * 3] = s_sfb;
            tab[s_node * 3 + 1] = s_sum;
            tab[s_node * 3 + 2] = s_sfe;
            leftright[s_node * 2] = s_ml;
            leftright[s_node * 2 + 1] = s_mr;
        }

        tab[0] = get<1>(res);
        tab[1] = get<0>(res);
        tab[2] = get<2>(res);
        leftright[0] = get<3>(res);
        leftright[1] = get<4>(res);


        int64 max_final = 0;

        for (int i = 0; i < nodes; i++)
        {
            for (int j = i; j < nodes; j++)
            {
                if (i == j)
                {
                    max_final = max(max_final, tab[i * 3 + 1]);
                }
                else
                {
                    int64 temp_r = tab[i * 3 + 2];
                    int64 temp_s = tab[i * 3 + 1];
                    int64 subs = max(temp_s + temp_r, leftright[i * 2 + 1]);
                    tab[i * 3 + 2] = subs;
                    tab[i * 3 + 1] = 0;

                    int64 temp_r_j = tab[j * 3];
                    int64 temp_s_j = tab[j * 3 + 1];
                    int64 subs_j = max(temp_s_j + temp_r_j, leftright[j * 2]);
                    tab[j * 3 ] = subs_j;
                    tab[j * 3 + 1] = 0;

                    int64 s = 0;

                    max_final = max(max_final, get<0>(compute_max_subarray<int64>(array_getter, i * 3, (j * 3 + 3))));

                    tab[j * 3 ] = temp_r_j;
                    tab[j * 3 + 1] = temp_s_j;
                    tab[i * 3 + 2] = temp_r;
                    tab[i * 3 + 1] = temp_s;
                }
            }
        }
        delete tab;
        cout << max_final << endl;
    }
}