#include <fstream>

using namespace std;
ifstream cin("flip.in");
ofstream cout("flip.out");
long long N,M,sumax,sum,sum2,i,j,v[18][18];
int main()
{
   cin>>N>>M;
   sumax=0;
   for(i=1;i<=N;i++)
    for(j=1;j<=M;j++)cin>>v[i][j];

   for(i=1;i<=N;i++)
   {sum=0;
    for(j=1;j<=M;j++)sum=sum+v[i][j];
    if(sum<0){for(j=1;j<=M;j++)v[i][j]=v[i][j]*(-1);}}




    for(j=1;j<=M;j++)
   {sum2=0;
    for(i=1;i<=N;i++)sum2=sum2+v[i][j];
    if(sum2<0){for(i=1;i<=N;i++)v[i][j]=v[i][j]*(-1);}}

    for(i=1;i<=N;i++)
    {for(j=1;j<=M;j++)sumax=sumax+v[i][j];
    }

cout<<sumax<<" ";



    return 0;
}