Generally, it is known that the set of even permutations coincides with the set of permutations that can be expressed as a product of 3-cycle permutations.

出处：https://atcoder.jp/contests/abc296/editorial/6133

看起来这是一个结论。这个结论是什么意思呢？又是怎么证明的呢？请指个路谢谢。/bx