l = input().split()
d = {i:l.count(i) for i in l}
n = len(d)
match n:
    case 1:
        print(l[0])
    case 2:
        a, b = set(l)
        print([a, b][d[a]>d[b]])
    case 3:
        print(6 - sum(map(int, l)))