A number is called faithful if you can write it as the sum of distinct powers of 7.
e.g., 2457 = 7 + 7^{2} + 7^{4 . }If we order all the faithful numbers, we get the sequence 1 = 7^{0}, 7 = 7^{1}, 8 = 7^{0} + 7^{1}, 49 = 7^{2}, 50 = 7^{0} + 7^{2} . . . 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 <= 10^{5}

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