#include <iostream>
#include <fstream>

using namespace std;
ifstream f("flip.in");
ofstream g("flip.out");

long long n,m,a[50][50];
void citire()
{
    f>>n>>m;
    for (int i=1;i<=n;i++)
        for (int j=1;j<=m;j++)
            f>>a[i][j];
}
void suma1()
{
    int s;
    for (int i=1;i<=n;i++)
    {
        s=0;
        for (int j=1;j<=m;j++)
            s=s+a[i][j];
        if (s<0)
            for (int l=1;l<=m;l++)
                a[i][l]=a[i][l]*(-1);
    }
    for (int j=1;j<=m;j++)
    {
        s=0;
        for (int i=1;i<=n;i++)
            s=s+a[i][j];
        if (s<0)
            for (int l=1;l<=n;l++)
                a[l][j]=a[l][j]*(-1);
    }
}
int suma2()
{
    int s=0;
    for (int i=1;i<=n;i++)
        for (int j=1;j<=m;j++)
            s=s+a[i][j];
    return s;
}
int main()
{
    citire();
    suma1();
    g<<suma2();
    return 0;
}