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