AT_past202010_a

a=input().split()
x=int(a[0])
y=int(a[1])
z=int(a[2])
if x>y>z:
    print("B")
elif x<y<z:
    print("B")
elif y<x<z:
    print("A")
elif y>z>z:
    print("A")
else:
    print("C")