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A number is called faithful if you can write it as the sum of distinct powers of 7.
e.g., 2457 = 7 + 72 + 74 . If we order all the faithful numbers, we get the sequence 1 = 70, 7 = 71, 8 = 70 + 71, 49 = 72, 50 = 70 + 72 . . . and so on.
Given some value of N, you have to find the N'th faithful number.
Example 1:
Input: N = 3 Output: 8 Explanation: 8 is the 3rd Faithful number.
Example 2:
Input: N = 7 Output: 57 Explanation: 57 is the 7th Faithful number.
Your Task:
You don't need to read input or print anything. Your task is to complete the function nthFaithfulNum() which takes an Integer N as input and returns the answer.
Expected Time Complexity: O(log(N))
Expected Auxiliary Space: O(log(N))
Constraints:
1 <= N <= 105
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