Problem:
Score : 300 points

Problem Statement

1000000000000001 dogs suddenly appeared under the roof of Roger's house, all of which he decided to keep. The dogs had been numbered 1 through 1000000000000001, but he gave them new names, as follows:

the dogs numbered 1,2,\cdots,26 were respectively given the names a, b, ..., z;

the dogs numbered 27,28,29,\cdots,701,702 were respectively given the names aa, ab, ac, ..., zy, zz;

the dogs numbered 703,704,705,\cdots,18277,18278 were respectively given the names aaa, aab, aac, ..., zzy, zzz;

the dogs numbered 18279,18280,18281,\cdots,475253,475254 were respectively given the names aaaa, aaab, aaac, ..., zzzy, zzzz;

the dogs numbered 475255,475256,\cdots were respectively given the names aaaaa, aaaab, ...;

and so on.

To sum it up, the dogs numbered 1, 2, \cdots were respectively given the following names:

a, b, ..., z, aa, ab, ..., az, ba, bb, ..., bz, ..., za, zb, ..., zz, aaa, aab, ..., aaz, aba, abb, ..., abz, ..., zzz, aaaa, ...

Now, Roger asks you:

"What is the name for the dog numbered N?"

Constraints

N is an integer.

1 \leq N \leq 1000000000000001

Input

Input is given from Standard Input in the following format:

N

Output

Print the answer to Roger's question as a string consisting of lowercase English letters.

Sample Input 1

2

Sample Output 1

b

Sample Input 2

27

Sample Output 2

aa

Sample Input 3

123456789

Sample Output 3

jjddja

Solution in Python (3.8.2) (judge verdict: Accepted)

import sys
input = sys.stdin.readline
sys.setrecursionlimit(10 ** 7)
import bisect
import numpy as np
import math
from collections import deque
from collections import defaultdict
from math import gcd


N = int(input())
M = 1000000000000001

k = 3
mini = 26*(1 - 26**(k-1)) / (1 - 26) + 1
maxi = mini + 26**k - 1

for k in range(100):
    mini = 26*(1 - 26**(k-1)) / (1 - 26) + 1
    maxi = mini + 26**k - 1

    if mini <= N <= maxi:
        keta = k
        nunkome = N - mini
        break

import string
alphabets = string.ascii_letters # a-z+A-Zをロード
characters = alphabets[:26]
def base_cvt(value, n=26):

    result = ''
    tmp = int(value)
    while tmp >= n:
        idx = tmp%n
        result =  characters[idx] + result
        tmp = int(tmp / n)
    idx = tmp%n
    result = characters[idx] + result
    return result

matsubi = base_cvt(nunkome)

num = k - len(matsubi)
print("a"*num + matsubi)