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

for (i=1;i<=n;i++)
{
s=0;
for (j=1;j<=m;j++)
s=s+a[i][j];
if (s<0)
for (j=1;j<=n;j++)
a[i][j]=a[i][j]*-1;
}


for (j=1;j<=m;j++)
{

s=0;
for (i=1;i<=n;i++)
s=s+a[i][j];


if (s<0)
for (i=1;i<=n;i++)
a[i][j]=a[i][j]*-1;

}


for (i=1;i<=n;i++)
for (j=1;j<=m;j++)
ss=ss+a[i][j];
g<<ss<<'\n';

 g.close();
 f.close();
    return 0;
}