def convertToTitle(self, n):
    """
    :type n: int
    :rtype: str
    """
    s = ""
    while (n > 0):
        d = (n % 26) - 1
        if d < 0:
            d = 25
        n = (n - 1) // 26
        s += chr(ord('A') + d)

    return s[::-1]