def next_in_chain(n):
    """
    Given a positive integer n, computes the next element of its "happy number chain", obtained by
    summing the squares of its digits.

    Does not validate its input.

    :param n: a positive integer.
    :return: the sum of the squares of the digits of n
    """
    digits = map(int, list(str(n)))
    squares_of_digits = map(lambda x: x * x, digits)
    return sum(squares_of_digits)
    

def chain(n):
    """
    Given a positive integer n, yields the entries of its happy number chain.

    Does not validate its input.

    :param n: a positive integer.
    """
    while True:
        yield n
        n = next_in_chain(n)


def is_happy(n):
    """
    A positive integer n is "happy" if its happy number chain ends in 1.

    Given a positive integer n, returns whether or not it is happy.

    Does not validate its input.

    :param n: a positive integer
    :return: True if n is happy, False otherwise.
    """
    seen_so_far = set()
    for element in chain(n):
        if element in seen_so_far:
            return False
        if element == 1:
            return True
        seen_so_far.add(element)


if __name__ == '__main__':
    for i in range(1001):
        if is_happy(i):
            print(i)