#include <iostream>
#include <fstream>
using namespace std;

int main ()
{
fstream f("flip.in", ios::in);
fstream g("flip.out", ios::out);
int n,m,A[17][17],i,j,S=0,k=1;
f>>n>>m;
for (i=1;i<=n;i++)
	for (j=1;j<=m;j++)
		f>>A[i][j];
for (;k!=0;)
{
k=0;
for (i=1;i<=n;i++)
	{for (j=1;j<=m;j++)
	  	 S=S+A[i][j];
	if (S<0) {for (j=1;j<=m;j++)
		          A[i][j]=0-A[i][j];
	        k=1;}
	S=0;
	}
for (j=1;j<=m;j++)
	{for (i=1;i<=n;i++)
	  	 S=S+A[i][j];
	if (S<0) {for (i=1;i<=n;i++)
		          A[i][j]=0-A[i][j];
	        k=1;}
	S=0;
	}
}
for (i=1;i<=n;i++)
	for (j=1;j<=m;j++)
		S=S+A[i][j];
g<<S;
g.close ();
}