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MOG Round #1Ended |
E - Lucky Numbers on MOG
Languages: C, C++, Java, Pascal, Haskell, Python, JavaScript, Tiger, C#
Time & Memory limits: (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.
Sample test(s)
Input
1
Output
4
Input
2
Output
7
Input
3
Output
44