The inputs of 102219F - Military Class do not follow the constraints given in the problem description. If you go to the problem page, you'll find that there will be $$$k$$$ lines containing two integers $$$u_i,v_i(1≤u_i,v_i≤n)$$$ after the first line. However, in some of the tests, many of the $$$u_i$$$ and $$$v_i$$$ are greater than $$$n$$$. You can verify this in coach mode or by writing an infinite loop to get TLE after encountering the invalid inputs.

I had to spend more time on this problem than necessary because of this. The inputs should be fixed so that those who may try to solve it in the future can have a better experience.