For an integer n, write a function to determine if it is a power of four. If so, your function should output "True". Otherwise, output "False".
An integer n is a power of four, if there exists an integer x such that n == 4^x.
输入描述:
Only 1 test case for each Input. Every test case is an integer.
输出描述:
Output "True" if n is the power of 4. Otherwise, output "False".
备注:
-2^31 <= n <= 2^31 - 1