Complement of Base 10 Integer

class Solution:
    def bitwiseComplement(self, n: int) -> int:
        mask = 2
        while mask <= n:
            mask <<= 1
        #return mask - 1 - n
        return (mask - 1) ^ n
        '''if n == 0:
            return 1
        bits = int(log(n, 2)) + 1
        return n ^ ((1<<bits) - 1)'''