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 Specification

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

Output Specification

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

Sample Input 1

1

Sample Output 1

4

Sample Input 2

2

Sample Output 2

7

Sample Input 3

3

Sample Output 3

44