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