a, b, c=map(int,input().split())
if a==b and b==c:
    print(a)
elif (a==b and b!=c)==True :
    print(c)
elif (c==b and b!=a)==True :
    print(a)
elif (c==a and c!=b)==True:
    print(b)
else:
    lista=[0,1,2,3]
    lista.pop(lista.index(a))
    lista.pop(lista.index(b))
    lista.pop(lista.index(c))
    print(lista[0])