#include <stdio.h>

using namespace std;
#define FOR(i,n) for (i=1;i<=n;i++)
#define FOR2(i,n,j,m) FOR(i,n) FOR (j,m)
int i,j,n,m,a[20][20],s,k;
int main()
{
    freopen ("flip.in","r",stdin);
    freopen ("flip.out","w",stdout);
    scanf ("%ld%ld",&n,&m);
    FOR2(i,n,j,m)
            scanf ("%ld",&a[i][j]);
    FOR (k,1000000)
    {
        FOR(i,n)
        {
            s=0;
            FOR (j,m)
                s+=a[i][j];
            if (s<0)
                FOR (j,m)
                    a[i][j]*=-1;
        }
        FOR(j,m)
        {
            s=0;
            FOR (i,n)
                s+=a[i][j];
            if (s<0)
                FOR (i,n)
                    a[i][j]*=-1;
        }

    }
    s=0;
    FOR2(i,n,j,m)
        s+=a[i][j];
    printf ("%ld",s);
    return 0;
}