def num2title(n: 'int > 0') ->str:
    """
    LeetCode 168: Excel Sheet Column Title
    Given a positive integer, return its corresponding column title as appear in an Excel sheet.
    """
    res = ''
    while n > 26:
        n, yu = divmod(n - 1, 26)
        res = chr(65 + yu) + res
    res = chr(64 + n) + res
    return res
