#include <fstream>

using namespace std;

ifstream f("flip.in");
ofstream g("flip.out");

int M[16][16],l[16],c[16],ok=1,aux,n,m,i,j;
long long S;

void afis() {
    for(int a=0;a<n;++a){
      for(int b=0;b<m;++b)
        g << M[a][b] << " ";
    g << "\n";}
    g << "\n";

}

int main()
{

    f >> n >> m;

    for(i=0;i<n;++i)
       for(j=0;j<m;++j){
        f >> M[i][j];
        l[i] += M[i][j];
        c[j] += M[i][j];
        }

    while(ok){ok = 0;

    for(i=0;i<n;++i)
     if(l[i]<0){ok=1; l[i]=0;
        for(j=0;j<m;++j){
            M[i][j]*= -1;
            l[i] += M[i][j];
            c[j] += 2*M[i][j];
            }
        }
    for(j=0;j<m;++j)
    if(c[j]<0){ok=1; c[j]=0;
        for(i=0;i<n;++i){
            M[i][j]*= -1;
            c[j] += M[i][j];
            l[i] += 2*M[i][j];
            }
       }
    }

    for(i=0;i<n;++i)
        for(j=0;j<m;++j)
         S += M[i][j];

    g << S;

    return 0;
}