#include <iostream>
#include <fstream>
using namespace std;
int main()

{
    int i,j,n,m,a[20][20],l[16],c[16],s=0,OK;
    fstream f("flip.in",ios::in);
    fstream g("flip.out",ios::out);
    f>>n>>m;
    for(i=1;i<=n;i++){ l[i]=0;c[i]=0;}

   for(i=1;i<=n;i++)
    for(j=1;j<=m;j++)
   {f>>a[i][j];
   l[i]=l[i]+a[i][j];
   c[j]=c[j]+a[i][j];}
OK=0;
do{OK=0;
   for(i=1;i<=n;i++)
   {if(l[i]<0)
    {for(j=1;j<=m;j++)
    a[i][j]=-a[i][j];
    OK=1;}}

    for(j=1;j<=m;j++)
    {if(c[j]<0)
    {for(i=1;i<=n;i++)
        a[i][j]=-a[i][j];
        OK=1;}
    }

}while(OK==0);


for(i=1;i<=n;i++)
    for(j=1;j<=m;j++)
    s=s+a[i][j];



g<<s;
cout<<s;


    g.close();
    f.close();
}