Is Power of Four

Determine whether a given integer is a power of four. A number is a power of four if it can be expressed as 4 raised to some integer exponent. Powers of four include 1, 4, 16, 64, and so on.

Examples
Input: 16
Output: true
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Is Power of Four

Determine whether a given integer is a power of four. A number is a power of four if it can be expressed as 4 raised to some integer exponent. Powers of four include 1, 4, 16, 64, and so on.