https://codeforces.com/problemset/problem/580/C
问从根节点到多少个叶子节点，满足路径上不出现超过m个连续的1
https://codeforces.com/problemset/problem/862/B
输出 (深度为奇数的点的个数) * (深度为偶数的点的个数) - 边数
https://codeforces.com/problemset/problem/1057/A
输入一棵树，找1到n路径上有哪些点
https://codeforces.com/problemset/problem/1176/E
任意找一颗树，选深度为奇数或者深度为偶数的所有点