def multiple(a, b):
    """Return the smallest number n that is a multiple of both a and b.

    >>> multiple(3, 4)
    12
    >>> multiple(14, 21)
    42
    """
    "*** YOUR CODE HERE ***"
    for i in range(min(a,b),0,-1):
        if a % i ==0 and b % i ==0:
            return a*b//i

def unique_digits(n):
    """Return the number of unique digits in positive integer n

    >>> unique_digits(8675309) # All are unique
    7
    >>> unique_digits(1313131) # 1 and 3
    2
    >>> unique_digits(13173131) # 1, 3, and 7
    3
    >>> unique_digits(10000) # 0 and 1
    2
    >>> unique_digits(101) # 0 and 1
    2
    >>> unique_digits(10) # 0 and 1
    2
    """
    "*** YOUR CODE HERE ***"
    ans=0
    for k in range(0,10,1):
        if has_digit(n,k):
            ans=ans+1;
    return ans

def has_digit(a,b):
    while a>0:
        if a % 10 ==b:
            return True
        a=a//10
    return False
