n = input()
ans = chr(ord("A") + n % 26)

if n >= 26:
  n -= 26
  i = 2
  while n >= 0:
    d = ((n % (26**i))) / (26**(i-1))
    ans += chr(ord("A") + d)
    n -= 26**i
    i += 1
print ans[::-1]