#include <iostream>
#include <fstream>
#include <cassert>
#include <cstdlib>
#include <algorithm>
#include <cstring>

int arr_sum(int *const arr, const int rows, const int cols) {
    int sum{0};
    for(int i = 0; i < rows; ++i) {
        for(int j = 0; j < cols; ++j) {
            sum += arr[i * cols + j];
        }
    }
    return sum;
}

void flip(int *const arr, const int rows, const int cols, const int row, const int col)
{
    for(int i = 0; i < rows; ++i) {
        arr[i * cols + col] *= -1;
    }
    for(int i = 0; i < cols; ++i) {
        arr[row * cols + i] *= -1;
    }
}

int main()
{
    std::fstream f("flip.in");
    assert(f.is_open());

    int rows, cols;
    f >> rows >> cols;

    assert(rows >= 1);
    assert(cols <= 16);

    int *arr = (int*)malloc(sizeof(int) * rows * cols);
    memset(arr, 0, sizeof(int)*rows*cols);

    for(int i = 0; i < rows * cols; ++i) {
        f >> arr[i];
    }
    f.close();
    
    int biggest = arr_sum(arr, rows, cols);
    for(int i = 0; i < rows; ++i) {
        for(int j = 0; j < cols; ++j) {
            flip(arr, rows, cols, i, j);
            int b = arr_sum(arr, rows, cols);
            if(b > biggest) {
                biggest = b;
            }
            flip(arr, rows, cols, i, j);
        }
    }
    
    std::ofstream o("flip.out");
    o << biggest;
    o.close();

    return 0;
}