prim #2 #4 两个-1点WA，求助求助

P1669 [USACO04DEC] Bad Cowtractors S

同求qwq
by MC_OIer @ 2023-11-07 21:29:49

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没输出-1。。。。。。
by MC_OIer @ 2023-11-07 21:41:19

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