#include <fstream>

using namespace std;
ifstream f("flip.in");
ofstream g("flip.out");
int main()
{long int N,M,a[100][100],i,j,s2=0,s1;
f>>N>>M;
for (i=1;i<=N;i++) {
    for (j=1;j<=M;j++) f>>a[i][j];
}
for (j=1;j<=M;j++) {s1=0;
    for (i=1;i<=N;i++) s1+=a[i][j];
    if (s1<0) {
        for (i=1;i<=N;i++) a[i][j]*=-1;
    }
}
for (i=1;i<=N;i++) {s1=0;
    for (j=1;j<=M;j++) s1+=a[i][j];
    if (s1<0) {
        for (j=1;j<=M;j++) a[i][j]*=-1;
    }
}

for (i=1;i<=N;i++) {
    for (j=1;j<=M;j++) s2+=a[i][j];
}
g<<s2;
}