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有9个环相互扣在了一起。每个环都标了号码,中间一环是9号。请你辨别一下,剪开几个环子(越少越好),所有的环子就都能完全分离开了?
There are nine rings clasped together. Each ring is marked with a number, the middle ring is No. 9. Please discern, cut a few rings (the less the better), all the rings can be completely separated?