a,b,c = map(int,input().split())
cnt = [0] * 4
cnt[a] += 1
cnt[b] += 1
cnt[c] += 1

if max(cnt) == 3:
    print(a)
elif max(cnt) == 2:
    for i in range(4):
        if cnt[i] == 1:
            print(i)
else:
    for i in range(4):
        if cnt[i] == 0:
            print(i)