#include<fstream.h>
int main()
{
int stop,l,c,i,j,s1,s2,t1,t2,a[17][17];
s2=t1=t2=0;
stop=1;
ifstream in("flip.in");
ofstream out("flip.out");
in>>l>>c;
for(i=1;i<=l;i++)
for(j=1;j<=c;j++)
in>>a[i][j];
while(stop!=0)
{
for(i=1;i<=l;i++)
{
s1=0;
for(j=1;j<=c;j++)
{
s1=s1+a[i][j];
t1+=a[i][j];
};
if(-s1>s1)
for(j=1;j<=c;j++)
a[i][j]=a[i][j]*-1;
};
for(j=1;j<=c;j++)
{
s1=0;
for(i=1;i<=l;i++)
s1=s1+a[i][j];
if(-s1>s1)
for(i=1;i<=l;i++)
a[i][j]=a[i][j]*-1;
};
if(t2==t1)
stop=0;
t2=t1;
t1=0;
};
for(i=1;i<=l;i++)
for(j=1;j<=c;j++)
s2+=a[i][j];
out<<s2;
in.close();
out.close();
return(0);
}