Matcom Online Grader

Digits $4$ and $7$ are lucky, while all others are unlucky. An integer is lucky if it contains only lucky digits in decimal notation. We would like to know the $K$-th lucky positive integer.

Input

The first and only line of input contains a positive integer $K$ $(1 \leq K \leq 10^9)$.

Output

The first and only line of output must contain the $K$-th lucky positive integer.

Sample test(s)