#include <iostream>
#include <fstream>

using namespace std;
ifstream fin("flip.in");
ofstream fout("flip.out");
int suma(int a,int b,int v[]){
    int S=0;
    for(int i=a;i<=b;++i)
        S+=v[i];
    return S;
}

int main()
{
    int a[100][100],m,n;
    fin>>n>>m;
    for(int i=1;i<=n;++i)
        for(int j=1;j<=m;++j)
            fin>>a[i][j];
    for(int i=1;i<=n;++i){
        if(suma(1,m,a[i])*(-1)>suma(1,m,a[i]))
            for(int j=1;j<=m;++j)
                a[i][j]*=(-1);
    }
    for(int j=1;j<=m;++j)
    {
        int S1=0,S2=0;
        for(int i=1;i<=n;++i)
        {
            S1+=a[i][j];
            S2+=(-1*a[i][j]);
        }
        if(S2>S1)
            for(int i=1;i<=n;++i)
                a[i][j]*=(-1);
    }
    int S=0;
    for(int i=1;i<=n;++i)
    {
        for(int j=1;j<=m;++j)
            S+=a[i][j];
    }
    cout<<S;
    fin.close();
    fout.close();
    return 0;
}