#include<fstream.h>
long double S=0;
long int a[17][17],v[17];
int i,j,n,m,ok=0;
int main ()
{
ifstream f("flip.in");
ofstream g("flip.out");
f>>n>>m;
for (i=1;i<=n;i++)
     for (j=1;j<=m;j++)
	      {f>>a[i][j];
	       a[i][0]+=a[i][j];
	       a[0][j]+=a[i][j];}
while (ok==0)
{
for (j=1;j<=m;j++)
     if (a[0][j]<0)
	 for (i=0;i<=n;i++)
	     {a[i][j]*=-1;
		a[i][0]+=2*a[i][j];}
for (i=1;i<=n;i++)
     if (a[i][0]<0)
	for (j=0;j<=m;j++)
	    {a[i][j]*=-1;
	     a[j][0]+=2*a[i][j];}
ok=1;
for (j=1;j<=m;j++)
     if (a[0][j]<0) ok=0;
for (i=1;i<=n;i++)
     if (a[i][0]<0) ok=0;
}
for (i=1;i<=n;i++)
    for (j=1;j<=n;j++) S=S+a[i][j];
g<<S;
f.close();
g.close();
return 0;
}