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