def join_institution(institution):
    if (len(institution) == 0):
        return None
    if (len(institution) == 1):
        return institution[0]
    res = ', '.join(institution[:(- 1)])
    res += (' and ' + institution[(- 1)])
    return res
def join_institution(institution):
    if (len(institution) == 0):
        return None
    if (len(institution) == 1):
        return institution[0]
    res = ', '.join(institution[:(- 1)])
    res += (' and ' + institution[(- 1)])
    return res