#int(input())
#map(int, input().split())
#list(map(int, input().split()))

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

a = sorted(a)

if a[0] == a[2]:
    print(a[0])
elif a[0] == a[1]:
    print(a[2])
elif a[1] == a[2]:
    print(a[0])
else:
    print(6 - sum(a))