#include "bits/stdc++.h"
using namespace std;
#define int long long
#define REP(i, n) for (int i = 0; i < (int)n; ++i)
#define RREP(i, n) for (int i = (int)n - 1; i >= 0; --i)
#define FOR(i, s, n) for (int i = s; i < (int)n; ++i)
#define RFOR(i, s, n) for (int i = (int)n - 1; i >= s; --i)
#define ALL(a) a.begin(), a.end()
#define IN(a, x, b) (a <= x && x < b)
template<class T>istream&operator >>(istream&is,vector<T>&vec){for(T&x:vec)is>>x;return is;}
template<class T>inline void out(T t){cout << t << "\n";}
template<class T,class... Ts>inline void out(T t,Ts... ts){cout << t << " ";out(ts...);}
template<class T>inline bool CHMIN(T&a,T b){if(a > b){a = b;return true;}return false;}
template<class T>inline bool CHMAX(T&a,T b){if(a < b){a = b;return true;}return false;}
constexpr int INF = 1e18;



signed main(){
	int N, M;
	cin >> N >> M;
	vector<int>a(M);
	cin >> a;
	REP(i, M) --a[i];
	vector<vector<int>>g(N);
	REP(i, N - 1) {
		int a, b;
		cin >> a >> b;
		--a; --b;
		g[a].emplace_back(b);
		g[b].emplace_back(a);
	}
	vector<int>dp(N); //falseは行動すると負け
	{
		auto dfs = [&](auto&&f, int now, int par) -> bool {
			int ret = 0, child = 0;
			for(auto e: g[now]) {
				if(e == par) continue;
				++child;
				if(f(f, e, now) == false) ret = true;
			}
			return dp[now] = ret;
		};
		dfs(dfs, 0, -1);
	}
	vector<int>v(N);
	vector<int>dp2(N);
	{
		auto dfs = [&](auto&&f, int now, int par, int par_val) -> void {
			//自分を親と見た時の結果を集計する
			int child = 0, end = 0;;
			for(auto e: g[now]) {
				if(e == par && par != -1){
					if(!par_val){
						++end;
						v[now] = par;
					}
					continue;
				}
				++child;
				if(!dp[e]){
					++end;
					v[now] = e;
				}
			}
			if(end)dp2[now] = true;
			for(auto e: g[now]) {
				if(e == par) continue;
				int flg = 0;
				if(end > 1)flg = true;
				else if(end == 1 && dp[e] == true) flg = true;
				else flg = false;
				f(f, e, now, flg);
			}
		};
		dfs(dfs, 0, -1, 0);
	}
	int ans = 0;
	REP(i, M) {
		if(dp[a[i]]) ans ^= 1;
	}
	if(ans == 0) out(-1, -1);
	else {
		REP(i, M) {
			if(dp[i] == false) continue;
			for(auto e: g[i]) {
				if(dp2[e] == true) {
					out(i + 1, v[i] + 1);
					exit(EXIT_SUCCESS);
				}
			}
		}
	}
}