H = {}
for i in range(3):
    h = int(input())
    H[i] = h

H = sorted(H.items(), key=lambda x: x[1])
for i in range(len(H)):
    if H[i][0] == 0:
        print("A")
    elif H[i][0] == 1:
        print("B")
    else:
        print("C")