#include <fstream>

using namespace std;

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

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

void afis(){
    for(i=0;i<n;++i){
        for(j=0;j<m;++j)
         g << M[i][j] << " ";
    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] *= -1;
             for(j=0;j<m;++j){
              M[i][j] *= -1;
              c[j] += 2*M[i][j];
                }

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