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

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