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For a double-edge first, there must be a directional scheme satisfies any two points up. That edge of the biuret point, the original image becomes a tree query can be split into two paths to go up the chain section and some go down, then they would make a number of side chain on both up or both down, two difference engage in an array of statistics about illegal if and only if one side has a value in two difference array

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CF704C

Each \ ((x_i | x_j) \ ) as a one-side \ ((I, J) \) , then it is possible to obtain a pile branched or cyclic (possibly self-loop), each block is apparent communication are independent, can communicate to determine the state of each block, and then go to a global backpack. then for each dp chain on the exclusive oR of each sub-tree and the upper chain \ (0/1 \) of program, as long as the transfer of their enumeration value of this point, the backpack and then combined value dp similar point on the line; dp as the ring, because it is a ring, that ring is broken chain, dp and a chain of exclusive oR \ (0/1 \) program, then the contribution dp finished chain is broken consideration that edge. specific implementation may require \ (y \ grave {i} \) point details

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