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 PyPy3 (7.3.0) (judge verdict: Runtime Error)

import sys
from io import StringIO
import unittest
import math

def resolve():
    n = int(input())

    alphabets = [chr(ord('a') + x) for x in range(26)]

    ans = []
    h = 0
    tmp = 0

    while 1:
        tmp += 26 ** h
        if n >= tmp:
            h += 1
        else:
            break

    for hh in range(h - 1, -1, -1):
        tmp = n // (26 ** hh)
        ans.append(alphabets[tmp - 1])
        n -= tmp * (26 ** hh)

    print(''.join(ans))


class TestClass(unittest.TestCase):
    def assertIO(self, input, output):
        stdout, stdin = sys.stdout, sys.stdin
        sys.stdout, sys.stdin = StringIO(), StringIO(input)
        resolve()
        sys.stdout.seek(0)
        out = sys.stdout.read()[:-1]
        sys.stdout, sys.stdin = stdout, stdin
        self.assertEqual(out, output)

    def test_入力例_1(self):
        input = """2"""
        output = """b"""
        self.assertIO(input, output)

    def test_入力例_2(self):
        input = """27"""
        output = """aa"""
        self.assertIO(input, output)

    def test_入力例_3(self):
        input = """123456789"""
        output = """jjddja"""
        self.assertIO(input, output)


if __name__ == "__main__":
    # unittest.main()
    resolve()