#include<iostream.h>
#include<fstream.h>
#include<math.h>
fstream f("flip.in",ios::in);
fstream g("flip.out",ios::out);
int main()
{
int n,s=0,m,v[1][16],i,j,neg,poz,p=0;
f>>n;
g<<" ";
f>>m;
for (i=1;i<=n;i++)
	       for (j=1;j<=n;j++)
			     f<<v[i][j]<<" ";
i=1;
while (i<=n)
{
neg=0;
poz=0;
	   for (j=1;j<=m;j++)
			   if(v[i][j]<0) neg++;
					 else poz++;
					 if (neg>poz) v[i][j]=(v[i][j])*(-1);
i++;
}
j=1;
while (j<=m)
{
neg=0;
poz=0;
for (i=1;i<=n;i++)
	       if (v[i][j]<0) neg++;
			      else poz++;
			      if (neg>poz) v[i][j]=(v[i][j])*(-1);
j++;
}
for (i=1;i<=n;i++)
	       for (j=1;j<=m;j++)
			      s=s+v[i][j];
g>>s;
return 0;
}