#include<iostream.h>
#include<fstream.h>
#include<math.h>
fstream f("flip.in",ios::in);
fstream g("flip.out",ios::out);
void main()
{
long n,s,m,v[100][100],i,j,neg,poz;
f>>n>>m;
for (i=1;i<=n;i++)
	       for (j=1;j<=n;j++)
			     f<<v[i][j]<<" ";
while (i<=n)
{
i=1;
neg=0;
poz=0;
	   for (j=1;j<=m;j++)
			   if(v[i][j]<0) neg++;
					 else poz++;
					 if (neg>poz) v[i][j]=fabs(v[i][j]);
i++;
}
while (j<=m)
{
j=1;
neg=0;
poz=0;
for (i=1;i<=n;i++)
	       if (v[i][j]<0) neg++;
			      else poz++;
			      if (neg>poz) v[i][j]=fabs(v[i][j]);
j++;
}
for (i=1;i<=n;i++)
	       for (j=1;j<=m;j++)
			      s=s+v[i][j];
g<<s;
}