### E - Lucky Numbers on MOG

##### Languages: C, C++, Java, JavaScript, ... (details)

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.

Input
1
Output
4
Input
2
Output
7
Input
3
Output
44