#include<iostream>
#include<fstream>

#define intrare "flip.in"
#define iesire "flip.out"

using namespace std;

int main() {
    ifstream f(intrare);
    ofstream g(iesire);

    int n, m, sum,sum2,sum1,ok1,ok2;
    f >> n >> m;
    int A[17][17];
    int B[2][17];
    sum = 0;
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++) {
            f >> A[i][j];
            sum += A[i][j];
        }
    sum = 0;

    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++) {
            sum1 = 0;
            sum2 = 0;
            ok1 = 0;
            ok2 = 0;
            for (int k = 0; k < m; k++)
                sum2 += A[i][k];
            for (int x = 0; x < n; x++)
                sum1 += A[x][j];
            if (sum1 < 0)
                ok1 = 1;
            if (sum2 < 0)
                ok2 = 1;
            if (ok1==1&&ok2==1)
                if (abs(sum1) > abs(sum2)) {
                    for (int w = 0; w < n; w++)
                        A[w][j] *= (-1);
                }
                else
                    for (int w = 0; w < m; w++)
                        A[i][w] *= (-1);
            else {
                if (ok1 == 1) {
                    for (int w = 0; w < n; w++)
                        A[w][j] *= (-1);
                }
                else if(ok2==1)
                    for (int w = 0; w < m; w++)
                        A[i][w] *= (-1);
            }

        }
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++)
            sum += A[i][j];

    g << sum;

    return 0;
}