#include<iostream>
#include<fstream>
using namespace std;
ifstream f("flip.in");
ofstream g("flip.out");
int main()
{
    int n,m,A[40][40],i,j,S=0;
    f>>n;
    f>>m;
    for(i=1;i<=n;i++){
    for(j=1;j<=m;j++){f>>A[i][j];S=S+A[i][j];}
    if(S<0){
        for(j=1;j<=m;j++){A[i][j]=A[i][j]*(-1);}
    }
    S=0;
    }
    for(j=1;j<=m;j++){
    for(i=1;i<=n;i++){
      S=S+A[i][j];
    }
    if(S<0){
        for(i=1;i<=n;i++){A[i][j]=A[i][j]*(-1);}
    }
    S=0;
    }
    for(i=1;i<=n;i++)
    for(j=1;j<=m;j++){S=S+A[i][j];}
    g<<S;
}