# -*- coding: utf-8 -*-
"""
No.327 アルファベット列
https://yukicoder.me/problems/no/327

"""
import sys
from sys import stdin
from itertools import accumulate
from bisect import bisect_right
input = stdin.readline


def solve(N):
    lut = [0]
    for i in range(1, 10):
        lut.append(26**i)

    acc = list(accumulate(lut))
    # print(acc)
    keta = bisect_right(acc, N)
    offset = N - acc[keta - 1]

    digits = []
    for _ in range(keta):
        digits.append(offset % 26)
        offset //= 26

    alp = ['A' for _ in range(keta)]
    ans = []
    for a, d in zip(alp, digits):
        ans.append(chr(ord(a) + d))
    ans.reverse()
    return ans


def main(args):
    N = int(input())
    ans = solve(N)
    print(*ans, sep='')


if __name__ == '__main__':
    main(sys.argv[1:])