#include <iostream>
#include <fstream>

using namespace std;
ifstream f("flip.in");
ofstream g("flip.out");
int main()
{
    int a[17][17],m,n;
    f>>n>>m;
    for(int i=1;i<=n;i++)
        for(int l=1;l<=m;l++)
            f>>a[i][l];
    for(int i=1;i<=n;i++)
    {
        int sp=0,sn=0;
        for(int l=1;l<=m;l++)
            if(a[i][l]>0)sp+=a[i][l];
            else sn+=a[i][l];
        if(sn*-1>sp)
            for(int l=1;l<=m;l++)a[i][l]*=-1;
    }
    int s=0;
    for(int i=1;i<=m;i++)
    {
        int sp=0,sn=0;
        for(int l=1;l<=n;l++)
            if(a[l][i]>0)sp+=a[l][i];
            else sn+=a[l][i];
        if(sn*-1>sp)
            for(int l=1;l<=n;l++){a[l][i]*=-1;s+=a[l][i];}
        else
            for(int l=1;l<=n;l++)s+=a[l][i];
    }
    g<<s;
    return 0;
}