#include<stdio.h>
FILE *f,*g;
int a[20][20],i,j,k=1,s,n,m;
void main()
{
f=fopen("flip.in","r");
g=fopen("flip.out","w");
fscanf(f,"%d",&n);
fscanf(f,"%d",&m);

for(i=1;i<=n;i++)
for(j=1;j<=m;j++)
fscanf(f,"%d",&a[i][j]);

while(k<=n)
{
s=0;
for(j=1;j<=m;j++)
s+=a[k][j];
if(s<0)for(i=1;i<=m;i++)a[k][i]=a[k][i]*-1;
k++;
}
k=1;s=0;
while(k<=m)
{s=0;
for(i=1;i<=n;i++)
s+=a[i][k];
if(s<0)for(j=1;j<=n;j++)a[j][k]=a[j][k]*-1;
k++;
}
s=0;
for(i=1;i<=n;i++)
for(j=1;j<=m;j++)
s+=a[i][j];
fprintf(g,"%d",s);

fclose(f);fclose(g);
}