#include <cstdio>
using namespace std;
FILE *f, *g;
int s,i,j,m,n,a[21][21];
int main()
{f=fopen ("flip.in","r");
g=fopen ("flip.out","w");
fscanf (f,"%d%d",&m,&n);
for (i=1;i<=n;++i)
for (j=1;j<=m;++j)
fscanf (f,"%d",&a[i][j]);
for (i=1;i<=m;++i)
{s=0;
for (j=1;j<=n;++j)
s=s+a[j][i];
if (s<0)
for (j=1;j<=n;++j)
a[j][i]=a[j][i]*-1;
}
for (i=1;i<=n;++i)
{s=0;
for(j=1;j<=m;++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 (i=1;i<=n;++i)
for (j=1;j<=m;++j)
s=s+a[i][j];
fprintf (g,"%d\n",s);
return 0;
}