def _checkFore(r, c, linko):
    """Checks if (r,c) lies on a forelink for a node."""
    initialNode = (r-c)//4

    if initialNode < 0:
        return False
    
    forelinks = linko[initialNode][2]
    if len(forelinks) == 0:
        return False

    maxForelink = max(forelinks)

    return 2*maxForelink > 2*initialNode + c