#include <fstream>
#include <iostream>
using namespace std;
fstream fin("flip.in",ios::in);
fstream fout("flip.out",ios::out);


int main()
{
    int n,m,v[16][16],x=0;
    fin>>n;
    fin>>m;



    for(int i=1;i<=n;i++)
      for (int j=1;j<=m;j++)
      fin>>v[i][j];
      int sem=1;

while(sem)
{
    sem=0;

    for(int i=1;i<=n;i++)
      { for (int j=1;j<=m;j++)   if(v[i][j]<0) x++;
         if(x>m/2)  { sem= 1;for (int j=1;j<=n;j++) v[i][j]= v[i][j] * (-1); }
       x=0;
      }
     for(int j=1;j<=n;j++)
      { for (int i=1;i<=m;i++)   if(v[i][j]<0) x++;
         if(x>m/2)  { sem = 1; for (int i=1;i<=n;i++) v[i][j]= v[i][j] * (-1); }
       x=0;
      }

}
int s=0;


    for(int i=1;i<=n;i++)
    for (int j=1;j<=m;j++)
      s=s+v[i][j];
      fout<<s;

fin.close();
fout.close();
    return 0;
}