# -*- coding: utf-8 -*-

N = int(input())

number_list = []
while True:
    number_list.append(N%26)
    N //= 26
    if N==0:
        break

chr_list = []
for i,n in zip(range(len(number_list)), number_list):
    c = chr(ord('A')+n) if i==0 else chr(ord('A')+n-1)
    chr_list.insert(0, c)
print(''.join(chr_list))