import unicodedata

n = int(input())

s = ord("A")

digit = 1

counter = []

while(True):
    counter.append(n%26)
    n = n//26
    if n == 0:
        break
if len(counter) > 1:
    counter[len(counter)-1] = counter[len(counter)-1] - 1


ans = ""
for number in counter:
    ans = chr( s + number) + ans

print(ans)