#include <fstream.h>
#include <iostream.h>
long a[17][17];
int n, m;

long reverse () {
    long sum;
    int i, j;
    
    for (i = 1; i <= n; i++) {
        sum = 0;
        for (j = 1; j <= m; j++) sum += a[i][j];
        if (sum < 0) {
            for (j = 1; j <= m; j++) a[i][j] *= -1;
        }
    }
    for (i = 1; i <= m; i++) {
        sum = 0;
        for (j = 1; j <= n; j++) sum += a[j][i];
        if (sum < 0) {
            for (j = 1; j <= n; j++) a[j][i] *= -1;
        }
    }
    
    sum = 0;
    for (i = 1; i <= n; i++)
        for (j = 1; j <= m; j++) sum += a[i][j];

    return sum; 
}

int main () {
    int i, j;
    
    ifstream inFile ("flip.in");
    inFile >> n >> m;
    for (i = 1; i <= n; i++)
        for (j = 1; j <= m; j++) inFile >> a[i][j];
    inFile.close ();

    ofstream outFile ("flip.out");
    outFile << reverse ();
    outFile.close ();
    
    return 0;
}