#include<fstream>
#include<iostream>
using namespace std;
int main ()
{int n,m,a[17][17],s=0,s1=0,i,j;
ifstream f("flip.in");
f>>n;
f>>m;
for (i=1;i<=n;i++)
	for (j=1;j<=m;j++)
	   f>>a[i][j];
for (i=1;i<=n;i++)
	{for (j=1;j<=m;j++)
	 {s1=s1+a[i][j];
	   if (s1<0)
	    {for (j=1;j<=m;j++)
		   a[i][j]=-a[i][j];
	    }
	 }
    s1=0;
	}	
for (j=1;j<=m;j++)
  {for (i=1;i<=n;i++)
	{s1=s1+a[i][j];
	  if (s1<0)
       {for (i=1;i<=n;i++)
	       a[i][j]=-a[i][j];
	   }
	}
	s1=0;
   }
for (i=1;i<=n;i++)
	for (j=1;j<=m;j++)
		s=s+a[i][j];
ofstream g("flip.out");
g<<s;
f.close();
g.close();
return 0;
}