#include <fstream>
#include <cmath>

using namespace std;

ifstream fin("flip.in");
ofstream fout("flip.out");

int main()
{
    int S=0,N,M,i,j,v[17][17],mini[17],minj[17],maxi[17],maxj[17];
    fin>>N>>M;
    for(i=1;i<=N;i++)
    {
        mini[i]=1000000;
        maxi[i]=-1000000;
    }
    for(j=1;j<=M;j++)
    {
        minj[j]=1000000;
        maxj[j]=-1000000;
    }
    for(i=1;i<=N;i++)
        for(j=1;j<=M;j++)
        {
            fin>>v[i][j];
            if(v[i][j]<mini[i])mini[i]=v[i][j];
            if(v[i][j]<minj[j])minj[j]=v[i][j];
            if(v[i][j]>maxj[j])maxj[j]=v[i][j];
            if(v[i][j]>maxi[i])maxi[i]=v[i][j];
        }
    for(j=1;j<=M;j++)
    {
        if(abs(minj[j])>maxj[j])
        {
            for(i=1;i<=N;i++)
                v[i][j]*=-1;
        }
    }
    for(i=1;i<=N;i++)
    {
        if(abs(mini[i])>maxi[i])
        {
            for(j=1;j<=M;j++)
                v[i][j]*=-1;
        }
    }
    for(i=1;i<=N;i++)
        for(j=1;j<=M;j++)
            S+=v[i][j];

    fout<<S;
    return 0;
}