#!/usr/bin/env python
# Solucao Tarefa Fliper
# OBI2014

P,R=raw_input().split()

P=int(P)
R=int(R)

if P == 0 and R == 0:
    print "C"
elif P == 0 and R == 1:
    print "C"
elif P == 1 and R == 0:
    print "B"
else:
    print "A"