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

if max(l) == 3:
    print(a)

elif max(l) == 2:
    for i in range(4):
        if l[i] == 1:
            ans = i
    print(ans)
else:
    for i in range(4):
        if l[i] == 0:
            ans = i
    print(ans)