# your code goes here
def quebracabecas(lista):
lista = sorted(lista)
teste_set = set(range(1,lista[-1]))
for i in lista:
if i in teste_set:
teste_set.remove(i)
return teste_set
print(quebracabecas([2, 4, 3])) # 1
print(quebracabecas([3, 1])) # 2
print(quebracabecas([2, 1])) # deveria retornar "3"
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