#include <fstream>
using namespace std;
int flip[17][17];
int main()
{
    int m,n,i,j,c,c1,s,s1;
    ifstream in("flip.in");
    ofstream out("flip.out");
    in>>n>>m;
    for (i=1;i<=n;i++)
    for (j=1;j<=m;j++)
    in>>flip[i][j];
    for (j=1;j<=m;j++)
    {
        c=c1=s=s1=0;
        for (i=1;i<=n;i++)
        if (flip[i][j]<0)
        s+=flip[i][j]*-1;
        else
        s1+=flip[i][j];
        if (s>s1)
        for (i=1;i<=n;i++)
        flip[i][j]*=-1;
    }
    for (i=1;i<=n;i++)
    {
        c=c1=s=s1=0;
        for (j=1;j<=m;j++)
        if (flip[i][j]<0)
        s+=flip[i][j]*-1;
        else
        s1+=flip[i][j];
        if (s>s1)
        for (j=1;j<=m;j++)
        flip[i][j]*=-1;
    }
    s=0;
    for (i=1;i<=n;i++)
    for (j=1;j<=m;j++)
    s+=flip[i][j];
    out<<s;
    in.close();
    out.close();
    return 0;
}