Sretan-COCI
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.
InputThe first and only line of input contains a positive integer K (1 <= K <= 10^9).
OutputThe first and only line of output must contain the K-th lucky positive integer.
Input:
1Output:
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