#include<iostream.h>
#include<fstream.h>
fstream in("flip.in",ios::in), out("flip.out",ios::out);
void suma(long int M[16][16],int&m,int i)
{ long s2=0,s1=0,j;
for(j=1;j<=m;j++)
if(M[i][j]>0) s1+=M[i][j];
else s2+=M[i][j];
s2=s2*-1;
if(s2>s1)
	for(j=1;j<=m;j++)
		M[i][j]=M[i][j]*-1;
}
void suma1(long int M[16][16],int&n,int j)
{ long s2=0,s1=0,i;
for(i=1;i<=n;i++)
if(M[i][j]>0) s1+=M[i][j];
else s2+=M[i][j];
s2=s2*-1;
if(s2>s1)
	for(i=1;i<=n;i++)
		M[i][j]=M[i][j]*-1;
}
int main()
{
long M[16][16],n,m,i,j,s=0;
in>>n>>m;
for(i=1;i<=n;i++)
for(j=1;j<=m;j++)
in>>M[i][j];
for(i=1;i<=n;i++)
suma(M,m,i);
for(j=1;j<=m;j++)
suma1(M,n,j);
for(i=1;i<=n;i++)
for(j=1;j<=m;j++)
s=s+M[i][j];
out<<s;
return 0;
}