#include <fstream>
using namespace std;
int main()
{
ifstream f("flip.in");
ofstream g("flip.out");
int n,m,s,i,j,l[100],c[100],a[100][100];
f>>n>>m;
for(i=1;i<=n;++i)
    for(j=1;j<=m;++j)
        {f>>a[i][j];
		l[i]=l[i]+a[i][j];}
for(i=1;i<=n;++i)
   {
    if(l[i]<0)
        for(j=1;j<=m;++j)
		a[i][j]=-a[i][j];}
for(i=1;i<=n;++i)
    {
    for(j=1;j<=m;++j)
	c[j]+=a[i][j];}
for(j=1;j<=m;++j)
   {
    if(c[j]<0)
        for(i=1;i<=n;++i)
	a[i][j]=-a[i][j];}
for(i=1;i<=n;++i)
    for(j=1;j<=m;++j)
	s+=a[i][j];
g<<s;
    return 0;
}