#include<fstream>
using namespace std;
int main()
{
    ifstream fin("flip.in");
    ofstream fout("flip.out");
    int n,m,i,j,snp,snn,t;
    fin>>n>>m;
    int a[n][m];
    for(i=1;i<=n;i++){
                      for(j=1;j<=m;j++){fin>>a[i][j];}
                      }
    for(i=1;i<=n;i++){
                      snp=snn=0;
                      for(j=1;j<=m;j++){
                                        if(a[i][j]>0){snp+=a[i][j];}
                                        else{snn+=a[i][j];}
                                        }
                      snn*=-1;
                      if(snn>snp){
                                  for(j=1;j<=m;j++){a[i][j]*=-1;}
                                  }
                      }
    
    for(j=1;j<=m;j++){
                      snp=snn=0;
                      for(i=1;i<=n;i++){
                                        if(a[i][j]>0){snp+=a[i][j];}
                                        else{snn+=a[i][j];}
                                        }
                      snn*=-1;
                      if(snn>snp){
                                  for(i=1;i<=n;i++){a[i][j]*=-1;}
                                  }
                      }
    
    t=0;
    for(i=1;i<=n;i++){
                      for(j=1;j<=m;j++){t+=a[i][j];}
                      }
    fout<<t;
    fin.close();
    fout.close();
}