#include <fstream>
#include<iostream>
using namespace std;
long c[16],l[16];
int main()
{
    ifstream in;in.open("flip.in");
    ofstream o;o.open ("flip.out", ofstream::out);
    long m,n,f[16][16],i,j,k;
    in>>n;in>>m;k=0;
    for(i=0;i<n;i++)
     for(j=0;j<m;j++)
        {
            in>>f[i][j];
            c[j]=c[j]+f[i][j];
            k=k+f[i][j];
            if(c[j]<0 && i==n-1)k=k-2*c[j];
        }
    for(j=0;j<m;j++)
        if(c[j]<0)
         for(i=0;i<n;i++)
            {
             f[i][j]= -f[i][j];
             l[i]=l[i]+f[i][j];
             if(l[i]<0){k=k-2*l[i];}
            }
        else
            for(i=0;i<n;i++)
            {
            l[i]=l[i]+f[i][j];
            if(l[i]<0)k=k-2*l[i];
            }
    o<<k;
    in.close();o.close();
   return 0;
}