#include <fstream>
#include <iostream>
#define N 20
using namespace std;

ifstream f("flip.in");
ofstream g("flip.out");
int t[N][N], n, m;

void citire(int t[][N], int n, int m)
{
    for(int i=1; i<=n; ++i)
        for(int j=1; j<=m; ++j)
            f>>t[i][j];
    f.close();
}

int main()
{
    f>>n>>m;
    citire(t, n, m);

    int s;
    for(int j=1;j<=m;++j)
    {
        s=0;
        for(int i=1;i<=n;++i)s+=t[i][j];
        if(s<0)
            for(int i=1;i<=n;++i)t[i][j]=-t[i][j];
    }

    for(int i=1;i<=n;++i)
    {
        s=0;
        for(int j=1;j<=m;++j)s+=t[i][j];
        if(s<0)
            for(int j=1;j<=m;++j)t[i][j]=-t[i][j];
    }

    s=0;
    for(int i=1;i<=n;++i)
        for(int j=1;j<=m;++j)s+=t[i][j];
    g<<s<<'\n';
    g.close();
    return 0;
}