# Task
 Consider the following algorithm for constructing 26 strings S(1) .. S(26):
```
S(1) = "a";
For i in [2, 3, ..., 26]:
S(i) = S(i - 1) + character(i) + S(i - 1).```
 For example:
```
S(1) = "a"
S(2) = S(1) + "b" + S(1) = "a" + "b" + "a" = "aba"
S(3) = S(2) + "c" + S(2) = "aba" + "c" +"aba" = "abacaba"
...
S(26) = S(25) + "z" + S(25)```
Finally, we got a long string S(26). Your task is to find the `k`th symbol (indexing from 1) in the string S(26). All strings consist of lowercase letters only.
# Input / Output
 - `[input]` integer `k`
  1 ≤ k < 2^(26)
 - `[output]` a string(char in C#)
  the `k`th symbol of S(26)
from string import ascii_lowercase

def abacaba(k):
    for i, c in enumerate(reversed(ascii_lowercase)):
        p = 2 ** (25 - i)
        if k == p:
            return c
        if k > p:
            k -= p

from string import ascii_lowercase

def abacaba(k):
    for i, c in enumerate(reversed(ascii_lowercase)):
        p = 2 ** (25 - i)
        if k == p:
            return c
        if k > p:
            k -= p
