Power of Four Exponent Finder

Given an integer (N), determine whether it is a power of four. If (N) is a power of four, find the non-negative integer (k) such that (4^k = N). Otherwise, output (-1).

The task is to read an integer from the standard input (stdin) and output the result to the standard output (stdout).

For example, if (N = 16), then (4^2 = 16) so the answer is 2. If (N = 15), since 15 is not a power of four, the answer should be (-1).

inputFormat

A single line containing an integer (N).

outputFormat

Output a single integer, which is the exponent (k) if (N) is a power of four (i.e. (4^k = N)); otherwise, output (-1).## sample

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