There is a treasure on an island. You see three islanders, big, medium and small. You know the big islander knows whether the treasure is on the mountain or under the mountain, but sometimes he tells the truth and sometimes he lies. Only the Chinese islanders know whether the big islanders are telling the truth or not, but the Chinese islanders themselves tell the truth when the previous person tells the truth and tell lies when the previous person tells lies. The two islanders use their left or right hands to say yes, but you don't know which hand says yes and which hand says no. Only people on the island know. But he always tells the truth or lies, and you don't know which of these two types he is. Can you ask whether the treasure is on the mountain or under the mountain with the least number of questions? Tip: If you ask an islander where the treasure is, he will ask how you know where it is. It is equal to asking for nothing. ) rigorous logical method answer, * * * four steps.

1. Ask the big islanders: Where is the treasure?

2. Ask China islanders: Is what the big islanders said true? (This step is crucial, because the big islanders tell the truth, and the China islanders also tell the truth, and he will raise his good hand. On the contrary, the big islanders lied, and so did the China islanders. He still raised his hand to say yes, so that we would know which hand of the China islanders said yes and which hand didn't. )

3. Ask the islanders: What do their two hands mean? (Because we already know what the two hands of China islanders mean, we can also judge whether what the islanders said is true or not, so we know whether what the big islanders just said is true or not. )

4. Ask China islanders: Is what the big islanders just said true? (At this time, knowing that what the islanders said is true or false, China islanders will follow suit and tell the truth and falsehood, and we will know that what the big islanders said is true or false. )