Base-2 Palindromes

A positive integer $N$ is a base-$b$ palindrome when the base-$b$ representation of $N$ reads the same forward and backward. For example, the decimal number 7 is a single digit in every base 8 or larger, so it is a palindrome in all of those bases. It is a palindrome in base 2 ($111$) and in base 6 ($11$) as well, but not in base 3 ($21$), base 4 ($13$), base 5 ($12$), or base 7 ($10$). Written in base 10 and sorted from smallest, the base-2 palindromes begin 1, 3, 5, 7.

Find the $M$-th base-2 palindrome and print it in base 10.

The first line contains one positive integer $M$ written in base 10. ($1 \le M \le 50000$)

Print the $M$-th base-2 palindrome in base 10 on the first line.