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//Maciej Poleski
#ifdef DEBUG
#define _GLIBCXX_CONCEPT_CHECKS
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <cassert>
namespace
{
namespace Wrapper
{
std::ifstream in;
std::ofstream out;
}
void init(int argc, char **argv)
{
    if (argc != 3)
    {
        std::cerr << "Potrzeba dokładnie dwóch argumentów\n";
        std::abort();
    }
    Wrapper::in.open(argv[1]);
    Wrapper::out.open(argv[2]);
}
}
#define check(x) assert(x)
#else
#ifndef NDEBUG
#define NDEBUG
#endif
#define check(x)
#include <iostream>
namespace
{
namespace Wrapper
{
std::istream &in = std::cin;
std::ostream &out = std::cout;
}
}
#endif

#include <cstdint>

namespace
{
namespace Wrapper
{
typedef std::uint_fast64_t uint_fast64_t;
typedef std::uint_fast32_t uint_fast32_t;
typedef std::uint_fast16_t uint_fast16_t;
typedef std::uint_fast8_t uint_fast8_t;

typedef std::uint64_t uint64_t;
typedef std::uint32_t uint32_t;
typedef std::uint16_t uint16_t;
typedef std::uint8_t uint8_t;

typedef std::int_fast64_t int_fast64_t;
typedef std::int_fast32_t int_fast32_t;
typedef std::int_fast16_t int_fast16_t;
typedef std::int_fast8_t int_fast8_t;

typedef std::int64_t int64_t;
typedef std::int32_t int32_t;
typedef std::int16_t int16_t;
typedef std::int8_t int8_t;

typedef std::size_t size_t;
}

}

#include <string>
#include <algorithm>
#include <limits>
#include <locale>
#include <cstring>
#include <utility>
#include <cstdlib>
#include <random>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include <list>
#include <iomanip>
#include <set>
#include <map>
#include <memory>
#include <functional>
#include <unordered_map>
#include <unordered_set>
#include <complex>
#include <type_traits>

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

namespace
{
using namespace Wrapper;

const int_fast64_t size = Size();
const auto numberOfNodes = NumberOfNodes();
const auto myNodeId = MyNodeId();

int_fast64_t singleMachineSolution()
{
    int_fast64_t bestSolution = 0;
    int_fast64_t currentSolution = 0;
    for (std::remove_const<decltype(size)>::type i = 1; i <= size; ++i)
    {
        int_fast64_t c = ElementAt(i);
        currentSolution += c;
        if (bestSolution < currentSolution)
            bestSolution = currentSolution;
        if (currentSolution < 0)
            currentSolution = 0;
    }
    return bestSolution;
}

inline static void solution()
{
    using std::swap;

    if (size < 1000)
    {
        if (myNodeId == 0)
        {
            out << singleMachineSolution() << '\n';
        }
    }
    else
    {
        long long bestSolution = 0;
        long long currentSolution = 0;
        long long bestLeft = 0;
        long long total = 0;
        for (auto i = 1 + size * myNodeId / numberOfNodes; i <= size * (myNodeId + 1) / numberOfNodes; ++i)
        {
            int_fast64_t c = ElementAt(i);
            total += c;
            if (bestLeft < total)
                bestLeft = total;
            currentSolution += c;
            if (bestSolution < currentSolution)
                bestSolution = currentSolution;
            if (currentSolution < 0)
                currentSolution = 0;
        }
        // Best right is *currentSolution*
        if (myNodeId != 0)
        {
            PutLL(0, bestSolution);
            PutLL(0, bestLeft);
            PutLL(0, total - bestLeft - currentSolution);
            PutLL(0, currentSolution);
            Send(0);
        }
        else
        {
            int_fast64_t *reduced = new int_fast64_t[numberOfNodes * 3];
            reduced[0] = bestLeft;
            reduced[1] = total - bestLeft - currentSolution;
            reduced[2] = currentSolution;
            for (int i = 1; i < numberOfNodes; ++i)
            {
                const auto sourceNode = Receive(-1);
                const long long rbest = GetLL(sourceNode);
                if (rbest > bestSolution)
                    bestSolution = rbest;
                reduced[3 * sourceNode] = GetLL(sourceNode);
                reduced[3 * sourceNode + 1] = GetLL(sourceNode);
                reduced[3 * sourceNode + 2] = GetLL(sourceNode);
            }
            // Classic algo
            currentSolution = 0;
            for (int i = 0; i < numberOfNodes * 3; ++i)
            {
                int_fast64_t c = reduced[i];
                currentSolution += c;
                if (bestSolution < currentSolution)
                    bestSolution = currentSolution;
                if (currentSolution < 0)
                    currentSolution = 0;
            }
            // End
            delete [] reduced;
            out << bestSolution << '\n';
        }
    }
}

} // namespace

int main(int argc, char **argv)
{
    std::ios_base::sync_with_stdio(false);
#ifdef DEBUG
    init(argc, argv);
#else
    (void)argc;
    (void)argv;
#endif
    solution();
    return 0;
}