N = long(raw_input())
if N < 26:
	print chr(ord('A') + N % 26)
else:
	s = chr(ord('A') + N % 26)
	N /= 26
	while True:
		if N < 26:
			s = chr(ord('A') + N % 26 - 1) + s
			break
		s = chr(ord('A') + N % 26 - 1) + s
		N /= 26
		N -= 1
	print s