#include <iostream>
#include <fstream>
using namespace std;
int n,i,j,m,a[20][20],s=0;
int main()
{
    ifstream f("filip.in");
    ofstream g("filip.out");
    f>>n;
    f>>m;
    for (i=1;i<=n;i++)
    {
        for (j=1;j<=m;j++)
        {
            f>>a[i][j];
        }
    }
    for (i=1;i<=n;i++)
    {
        for (j=1;j<=m;j++)
        {
            s=s+a[i][j];
            if (s<0)
            {
                for (i=1;i<=n;i++)
                {
                    a[i][j]=a[i][j]*-1;
                }
            }
            s=0;
        }
    }
    for (j=1;j<=m;j++)
    {
        for (i=1;i<=n;i++)
        {
            s=s+a[i][j];
            if (s<0)
            {
                for (j=1;j<=m;j++)
                {
                    a[i][j]=a[i][j]*-1;
                }
            }
            s=0;
        }
    }
    for (i=1;i<=n;i++)
    {
        for (j=1;j<=m;j++)
        {
            s=s+a[i][j];
        }
    }
    g<<s;
    return 0;
}