#include <bits/stdc++.h>

using namespace std;

int n,m,x[16][16],a,b;

ofstream out("flip.out");
ifstream in("flip.in");

int main()
{
    in >> n >> m;

    for(int i = 0;i<n;i++)
        for(int j = 0;j<m;j++)
            in >> x[i][j];

    for(int i = 0;i<n;i++) {
        a = 0;
        b = 0;
        for(int j = 0;j<m;j++) {
            if(x[i][j] < 0) a += x[i][j];
            else b += x[i][j];
        }
        if(a + b > 0) {
            for(int j = 0;j<m;j++) x[i][j] *= -1;
        }
    }

    for(int i = 0;i<m;i++) {
        a = 0;
        b = 0;
        for(int j = 0;j<n;j++) {
            if(x[j][i] < 0) a += x[j][i];
            else b += x[j][i];
        }
        if(a + b > 0) {
            for(int j = 0;j<n;j++) x[j][i] *= -1;
        }
    }
    a = 0;
    for(int i = 0;i<n;i++)
        for(int j = 0;j<m;j++)
            a+=x[i][j];
    if(a < 0) a*=-1;
    out << a;

    return 0;
}