#include<stdio.h>
int main()
{    freopen("flip.in","r",stdin);
     freopen("flip.out","w",stdout);
    int v[20][20],n,m,z=0,done=0,q;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++)
    for(int i2=1;i2<=m;i2++)
    scanf("%d",&v[i][i2]);
          while(done==0)
          {    done=1;
               for(int i=1;i<=n;i++)
               {
               q=0;
               for(int i2=1;i2<=m;i2++)
               {
                    q=v[i][i2]+q;
               }
               if(q<0)
               for(int i3=1;i3<=m;i3++)
               {
               v[i][i3]=-v[i][i3];
               done=0;
               }
               }
               for(int i=1;i<=m;i++)
               {
                    q=0;
               for(int i2=1;i2<=n;i2++)
               {
               {
                    q=v[i][i2]+q;
               }
               if(q<0)
               for(int i3=1;i3<=n;i3++)
               {
               v[i][i3]=-v[i][i3];
               done=0;
               }
               }
          }
          }
          for(int i=1;i<=n;i++)
          for(int i2=1;i2<=m;i2++)
          z=z+v[i][i2];
          printf("%d",z);

}