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

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

int main()
{
    int n, m,a[101][101];
    in>>n>>m;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++)
            in>>a[i][j];
    int s, mn = 0, indl = 0;
    for(int i=1;i<=n;i++){
        s = 0;
        for(int j=1 ; j<=m; j++)
            if(a[i][j] < 0)
                s += a[i][j];
        if(s < mn){
            mn = s;
            indl = i;
        }
    }
    int indc = 0;
    mn = 0;
    for(int i=1;i<=m;i++){
        s = 0;
        for(int j=1 ; j<=n; j++)
            if(a[j][i] < 0)
                s += a[j][i];
        if(s < mn){
            mn = s;
            indc = i;
        }
    }

    for(int i=1; i<=n; i++)
        a[i][indc] *= -1;
    for(int j=1; j<=m; j++)
        a[indl][j] *= -1;
    s = 0;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++)
            s += a[i][j];
    out<<s<<endl;
    return 0;
}