alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
n = int(input())
digit = [0]
al_list = [0]
while n // 26 > 0:
    al_list = digit + al_list
    al_list[0] = n // 26
    al_list[1] = n % 26
    n //= 26
al_list[0] -= 1
for j in al_list:
    print(alphabet[j], end = '')