def parimpar(num):
    '''Devuelve par o impar.

    >>> parimpar(1)
    'impar'
    >>> parimpar(2)
    'par'
    >>> parimpar("2")
    'par'
    >>> parimpar("foo")
    Traceback (most recent call last): 
    ...
    ValueError: invalid literal for int() with base 10: 'foo'
    '''

    if int(num) % 2:
        return "impar"
    else:
        return "par"


if __name__ == "__main__":
    import doctest
    doctest.testmod()