solver

FIRST_TEN = ["one", "two", "three", "four", "five", "six", "seven",
             "eight", "nine"]
SECOND_TEN = ["ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen",
              "sixteen", "seventeen", "eighteen", "nineteen"]
OTHER_TENS = ["twenty", "thirty", "forty", "fifty", "sixty", "seventy",
              "eighty", "ninety"]
HUNDRED = "hundred"

ZERO = "ZERO"

def checkio(number):
    if number == 0:
        return ZERO
    if number < 10:
        return FIRST_TEN[number - 1]
    if number <  20:
        return SECOND_TEN[number - 10]
    if number < 100:
        other = checkio(number % 10)
        return (OTHER_TENS[(number // 10) - 2] + " " + other) if other != 'ZERO' else OTHER_TENS[(number // 10) - 2]
    if number < 1000:
        other = checkio(number % 100)
        return checkio(number // 100) + " " + HUNDRED if other == ZERO else checkio(number // 100) + " " + HUNDRED + " " + other