a = list(map(int,input().split()))
b = list(map(int,input().split()))
c = list(map(int,input().split()))

dct = {'A':a, 'B':b, 'C':c}


hls = list(set([a[0], b[0], c[0]]))
wls = list(set([a[1], b[1], c[1]]))
wls.sort()
hls.sort()
hls.reverse()

for i in hls:
    key = [j for j, k in dct.items() if k[0] == i]
    if len(key) == 1:
        print(key[0])
    elif len(key) >= 1:
        for l in wls:
            key = [j for j,k in dct.items() if k[0] == i and k[1] == l ]
            if key == []:
                pass
            else:
                print(key[0])