#include <iostream>
#include <fstream>
using namespace std;

int main ()
{
    int M, N;
    int sum_col = 0, sum_row = 0, sum = 0;
    int **A;
    ifstream ifile ("flip.in");
    ofstream ofile ("flip.out");

    ifile >> N;
    ifile >> M;

    A = new int*[N];
    for (int i = 0; i < N; i++)
        A[i] = new int [M];

    for (int i = 0; i < N; i++)
        for (int j = 0; j < M; j++)
            ifile >> A[i][j];

    for (int i = 0; i < N; i++)
    {
        for (int j = 0; j < M; j++)
        {
            sum_row = sum_row + A[i][j];
        }
        if (sum_row < 0)
        {
            for (int j = 0; j < M; j++)
            {
                A[i][j] = (-1)*A[i][j];
            }
        }
        sum_row = 0;
    }

    for (int i = 0; i < M; i++)
    {
        for (int j = 0; j < N; j++)
        {
            sum_col = sum_col + A[j][i];
        }
        if (sum_col < 0)
        {
            for (int j = 0; j < N; j++)
            {
                A[j][i] = (-1)*A[j][i];
            }
        }
        sum_col = 0;
    }

    for (int i = 0; i < N; i++)
        for (int j = 0; j < M; j++)
            sum = sum + A[i][j];

    ofile << sum;
        

}