#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("flip.in");
ofstream fout("flip.out");
int main()
{
    int n,m,a[12][18],i,j,s1,s2,s;
    fin>>n;
    fin>>m;
    for(i=1;i<=n;i++)
        for(j=1;j<=m;j++)
            fin>>a[i][j];
    for(i=1;i<=n;i++)
    {
        s1=0;
        s2=0;
        for(j=1;j<=m;j++)
        {
            s1=a[i][j];
            s2=a[i][j]*-1;
        }
        if(s2>s1)
            for(j=1;j<=m;j++)
                a[i][j]=a[i][j]*-1;
    }
    for(j=1;j<=m;j++)
    {
        s1=0;
        s2=0;
        for(i=1;i<=n;i++)
        {
            s1=a[i][j];
            s2=a[i][j]*-1;
        }
        if(s2>s1)
            for(i=1;i<=n;i++)
                a[i][j]=a[i][j]*-1;
    }
    s=0;
    for(i=1;i<=n;i++)
        for(j=1;j<=m;j++)
            s=a[i][j]+s;
    fout<<s;
    return 0;
}