#include <iostream>
#include<fstream>
using namespace std;
ifstream f("flip.in");
ofstream g("flip.out");
int main()
{
    int n,m,a[100][100],i,j,s1,s=0;
    f>>n>>m;
    for(i=0,s1=0;i<n;i++,s1=0){
        for(j=0;j<m;j++){
            f>>a[i][j];
            s1+=a[i][j];
        }
        if(s1<0)
            for(j=0;j<m;j++)
                a[i][j]*=-1;
    }
    for(j=0;j<m;s1=0,j++){
        for(i=0,s1=0;i<n;i++)
            s1+=a[i][j];
        if(s1<0)
            for(i=0;i<n;i++)
                a[i][j]*=-1;
    }
        for(i=0;i<n;i++)
            for(j=0;j<m;j++)
                s+=a[i][j];
        g<<s;
    return 0;
}