#include <iostream>
#include<fstream>
#define FOR(i,a,b) for(i=a;i<=b;i++)
using namespace std;
ifstream f("flip.in");
ofstream g("flip.out");
int n,m,a[20][20],i,j,s,s2,sol,p;
int main()
{ f>>n>>m;
    FOR(i,1,n) FOR(j,1,m)f>>a[i][j];
   FOR(i,1,n){ s=0;
    FOR(j,1,m)
     s+=a[i][j];
     if(s<0)
         FOR(p,1,m)a[i][p]=-a[i][p];
   }
   FOR(j,1,m)
   { s=0;
       FOR(i,1,n)s+=a[i][j];
       if(s<0)FOR(p,1,n)a[p][j]=-a[p][j];
   }
   FOR(i,1,n)FOR(j,1,m)sol+=a[i][j];
   g<<sol;

    return 0;
}