def get_cyclic_label(cycle_nr):
    """
    Return string to be inserted in the SMILES string to indicate a cycle

    Input
    ----------
    cycle_nr: int, number of the cycle to be closed

    Output
    -------
    str, string to be inserted in the SMILES string to indicate a cycle

    """
    if cycle_nr > 9:
        return '%' + str(cycle_nr)
    else:
        return str(cycle_nr)