# https://leetcode.com/problems/integer-to-english-words
LOCALE = ['Zero', 'One', 'Two', 'Three', 'Four', 'Five', 'Six', 'Seven', 'Eight', 'Nine', 'Ten', 'Eleven', 'Twelve', 'Thirteen', 'Fourteen', 'Fifteen', 'Sixteen', 'Seventeen', 'Eighteen', 'Nineteen']
LOCALE_TEN = ['empty', 'empty', 'Twenty', 'Thirty', 'Forty', 'Fifty', 'Sixty', 'Seventy', 'Eighty', 'Ninety']
HUNDRED = 'Hundred'
LOCALE_UNIT = ['Thousand', 'Million', 'Billion', 'Trillion']
UNIT = 1000
class Solution:
    def numberToWords(self, num: int) -> str:
        stack = []
        while num >= UNIT:
            stack.append(num % UNIT)
            num //= UNIT
        stack.append(num % UNIT)
        result = []
        def translate(val: int):
            if val == 0:
                result.append(LOCALE[val])
                return
            if val >= 100:
                result.append(LOCALE[val // 100])
                result.append(HUNDRED)
                val %= 100
            if val >= 20:
                result.append(LOCALE_TEN[val // 10])
                val -= (val // 10) * 10
            if val == 0:
               return
            result.append(LOCALE[val])
        while len(stack) > 0:
            translate(stack.pop())
            if len(stack) > 0:
                result.append(LOCALE_UNIT[len(stack) - 1])
        return ' '.join(result)