#include <iostream>
#include <fstream>
using namespace std;
int v[290][290];
int main()
{ifstream fin("flip.in");
ofstream fout("flip.out");
unsigned N,M,S,i,j,S1,S2;
int x;
fin>>N>>M;
S=0;
for (i=1;i<=N;i++)
  {S1=0;
   S2=0;
   for (j=1;j<=M;j++)
      {fin>>x;
       v[i][j]=x;
       if (x<0)
         S1=S1-x;
       else
         S2=S2+x;
      }
   if (S1>S2)
     for (j=1;j<=M;j++)
        {v[i][j]=-v[i][j];
        }

  }
for (j=1;j<=M;j++)
   {S1=0;
    S2=0;
    for (i=1;i<=N;i++)
       {if (v[i][j]<0)
         S1=S1-v[i][j];
       else
         S2=S2+v[i][j];
       }
    if (S1>S2)
     for (i=1;i<=N;i++)
        {v[i][j]=-v[i][j];
        }
   }
for (i=1;i<=N;i++)
   {for (j=1;j<=M;j++)
       {S=S+v[i][j];
       }
   }
fout<<S;
fin.close();
fout.close();
return 0;
}