Given an integer `n`

, return * true if it is a power of four. Otherwise, return false*.

An integer `n`

is a power of four, if there exists an integer `x`

such that `n == 4`

.^{x}

**Example 1:**

Input:n = 16Output:true

**Example 2:**

Input:n = 5Output:false

**Example 3:**

Input:n = 1Output:true

**Constraints:**

`-2`

^{31}<= n <= 2^{31}- 1

class Solution {
public boolean isPowerOfFour(int n) {
}
}