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# Problem ESretan

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 $K$ ($1 \le K \le 10^9$).

## Output

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

Sample Input 1 Sample Output 1
1

4

Sample Input 2 Sample Output 2
2

7

Sample Input 3 Sample Output 3
3

44