#include <cstdio>
using namespace std;
FILE *f=fopen("flip.in","r");
FILE *g=fopen("flip.out","w");
int v[17][17];bool ok;
int main()
{int n,m,i,j;
long long s;
fscanf(f,"%d %d",&n,&m);
for (i=1;i<=n;i++) for (j=1;j<=m;j++) fscanf(f,"%d",&v[i][j]);
do
{ok=false;
for (i=1;i<=n;i++) {s=0;
                    for (j=1;j<=m;j++) s+=v[i][j];
                    if (s<0) {for (j=1;j<=m;j++) v[i][j]=-v[i][j];
                              ok=true;}
                    }
for (j=1;j<=m;j++) {s=0;
                    for (i=1;i<=n;i++) s+=v[i][j];
                    if (s<0) {for (i=1;i<=n;i++) v[i][j]=-v[i][j];
                              ok=true;  }
                    }
}while (ok==true);
s=0;
for (i=1;i<=n;i++) for (j=1;j<=m;j++) s+=v[i][j];
fprintf(g,"%lld",s);
return 0;
}