#include <bits/stdc++.h>
using namespace std;
const int NR = 510000;
int nxt[NR], to[NR], head[NR], wid[NR], tot;
int dep[NR], fa[NR][30], lg[NR];

void add(int x, int y)
{
	to[++tot] = y;
	nxt[tot] = head[x];
	head[x] = tot;
}

void dfs(int now, int fath)
{
	fa[now][0] = fath;
	dep[now] = dep[fath] + 1;
	for (int i = 1; i <= 25; ++i)
		fa[now][i] = fa[fa[now][i - 1]][i - 1];
	for (int i = head[now]; i; i = nxt[i])
		if (to[i] != fath)
			dfs(to[i], now);
}

int LCA(int x, int y)
{
	int cnt1 = 0, cnt2 = 0;
	if (dep[x] > dep[y]) {
		while (dep[x] > dep[y]) {
			x = fa[x][lg[dep[x] - dep[y]]];
			cnt1 += (1 << (lg[dep[x] - dep[y]]));
		}
	} else {
		while (dep[x] < dep[y]) {
			y = fa[y][lg[dep[y] - dep[x]]];
			cnt2 += (1 << (lg[dep[y] - dep[x]]));
		}
	}
	if (x == y)
		return (cnt1 * 2) + cnt2;
	for (int k = 25; k >= 0; --k)
		if (fa[x][k] != fa[y][k]) {
			x = fa[x][k], y = fa[y][k];
			cnt1 += (1 << k);
			cnt2 += (1 << k);
		}
	return (cnt1 * 2) + cnt2;
}

int main()
{
	int n, ans1 = 0, ans2 = 0, ans3, u, v;
	cin >> n;
	for (int i = 1; i < n; i++) {
		int x, y;
		cin >> x >> y;
		add(x, y);
		add(y, x);
	}
	lg[0] = 1;
	for (int i = 1; i <= n; i++)
		lg[i] = lg[i / 2] + 1;
	dfs(1, 0);
	for (int i = 1; i <= n; i++) {
		wid[dep[i]]++;
	}
	for (int i = 1; i <= n; i++) {
		ans1 = max(ans1, dep[i]);
		ans2 = max(ans2, wid[i]);
	}
	cin >> u >> v;
	ans3 = LCA(u, v);
	cout << ans1 << endl << ans2 << endl << ans3;
	return 0;
}

样例过了 但只有30pts #4 #5 #10 AC了，其他都WA王子了