def find_layer_id(layers_range, router_id):
    """
    Find layer id of the router.

    Parameters
    ----------
    layers_range : [type]
        list of router id range
    router_id : int
        [description]

    Returns
    -------
    int
        layer id
    """
    for itr, layer_range in enumerate(layers_range):
        if router_id in layer_range:
            return itr