Vigil

def is_positive(n):
    swear n > 0
    return n > 0

def factorial(n):
    implore n >= 0
    swear __result >= 1

    if n == 0:
        return 1

    return n * factorial(n - 1)

def fizzbuzz(n):
    implore n > 0

    i = 1
    while i <= n:
        if i % 15 == 0:
            print "FizzBuzz"
        elif i % 3 == 0:
            print "Fizz"
        elif i % 5 == 0:
            print "Buzz"
        else:
            print i
        i = i + 1

fizzbuzz(20)