HW = []
for _ in range(3):
    h, w = map(int, input().split())
    HW.append((h, w))
sorted_HW = sorted(HW, key=lambda x: (-x[0], x[1]))
# print('HW', HW)

for h, w in sorted_HW:
    for i, hw in enumerate(HW):
        _h, _w = hw
        if h == _h and w == _w:
            print('ABC' [i])