Problems
Ones and sevens
Ones and sevens
Find the n-th number of the increasing sequence of positive integers:
1 7 11 17 71 77 111 117 171 177 711 717..
Input
One positive integer n (1 ≤ n ≤ 107
).
Output
Print thee n-th number of the given sequence.
Input example #1
7
Output example #1
111