If n has exactly one bit set (i.e. it is a power of two), output the 1-indexed position of that bit counting from the least significant bit (so 1 -> position 1, 2 -> position 2, 4 -> position 3). Otherwise output -1.
Input format
One line: a positive integer n.
Output format
One line: the 1-indexed position of the single set bit, or -1.
Constraints
- 1 <= n <= 1000000000