alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
n = int(input())
digit = [0]
al_list = [n]
while al_list[0] // 26 > 0:
    al_list = digit + al_list
    al_list[0] = al_list[1] // 26 -1
    al_list[1] = al_list[1] % 26

for j in al_list:
    print(alphabet[j], end = '')