# 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()}



def solve(N):
    ans = chr(N % 26 + 65)
    while N >= 26:
        N = N // 26 - 1
        ans += chr(N % 26 + 65)
    return ans[::-1]

def main():
    N = II()
    print(solve(N))

if __name__ == "__main__":
    main()