#include <bits/stdc++.h>
using namespace std;

int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0), cout.tie(0);

	int n, m;
	cin >> n >> m;

	vector<int>adj[n + 1];
	for (int i = 0, u, v; i < n - 1; i ++) {
		cin >> u >> v;
		adj[u].push_back(v);
	}

	queue<int>q;
	for (int i = 0, d; i < m; i++) {
		cin >> d;
		q.push(d);
	}

	for (int i = 1; i <= n; i++)
		sort(adj[i].begin(), adj[i].end());
		
	int ans = 0;
	function<void(int)> dfs =[&] (int u)
	{
		// cout << u << " " << q.front() << endl;
		if(u == q.front()) {
			q.pop();
			ans++;
		}
		for (auto it : adj[u]) {

			dfs(it);
		if(u == q.front()) {
			q.pop();
			ans++;
		}
		
		}
	
		

	};
	
	dfs(1);
	cout << ans << endl;

	return 0;
}