#include <iostream>
#include <fstream>
std::ifstream f("flip.in");
std::ofstream g("flip.out");

int col(int a, int p, int x[17][17]){
    int s = 0;
    for(int i = 1; i <= a; i++)
        s = s + x[i][p];
    return s;
}

int ran(int a, int p, int x[17][17]){
    int s = 0;
    for(int j = 1; j <= a; j++)
        s = s + x[p][j];
    return s;
}

int sch(int x[17][17], int p, int k){
    for(int i = 1; i <= p; i++)
        x[i][k] = x[i][k] * -1;
    return x[17][17];
}

int sch1(int x[17][17], int p, int k){
    for(int i = 1; i <= p; i++)
        x[k][i] = x[k][i] * -1;
    return x[17][17];
}

int main(){
    int n, m, a[17][17], s;
    f >> n >> m;
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= m; j++)
            f >> a[i][j];
    for(int i = 1; i <= n; i++){
        s = ran(m, i, a);
        if(s < 0)
            sch1(a, n, i);
    }
    for(int i = 1; i <= n; i++){
        s = col(n, i, a);
        if(s < 0)
            sch(a, n, i);
    }
    s = 0;
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= m; j++)
            s = s + a[i][j];
    g << s;
    return 0;
}