# coding: utf-8
import array, bisect, collections, heapq, itertools, math, random, re, string, sys, time
sys.setrecursionlimit(10 ** 7)
inf = 10 ** 20
mod = 10 ** 9 + 7

def II(): return int(input())
def ILI(): return list(map(int, input().split()))
def IAI(LINE): return [ILI() for __ in range(LINE)]
def IDI(): return {key: value for key, value in ILI()}


N = II()

alph_list = [chr(i) for i in range(65, 65 + 26)]


def main():
    ans = collections.deque()
    first_char = alph_list[N % 26]
    ans.append(first_char)

    if N // 26 > 0:
        now_num = N // 26
        while True:
            next_div = now_num // 26
            next_char = alph_list[now_num % 26 - 1]
            ans.appendleft(next_char)
            
            if next_div == 0:
                break
            
            now_num = next_div

    return "".join(list(ans))


if __name__ == "__main__":
    print(main())