342\. Power of Four

Easy

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 <code>n == 4<sup>x</sup></code>.

**Example 1:**

**Input:** n = 16

**Output:** true 

**Example 2:**

**Input:** n = 5

**Output:** false 

**Example 3:**

**Input:** n = 1

**Output:** true 

**Constraints:**

*   <code>-2<sup>31</sup> <= n <= 2<sup>31</sup> - 1</code>

**Follow up:** Could you solve it without loops/recursion?