#include <bits/stdc++.h>
 
using namespace std;
 
#define DEBUG(x) cerr<<#x<<": "<<x<<endl;
#define DEBUG_VEC(v) cerr<<#v<<":";for(int i=0;i<v.size();i++) cerr<<" "<<v[i]; cerr<<endl;
#define DEBUG_MAT(v) cerr<<#v<<endl;for(int i=0;i<v.size();i++){for(int j=0;j<v[i].size();j++) {cerr<<v[i][j]<<" ";}cerr<<endl;}
typedef long long ll;
// #define int ll
 
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
#define pii pair<int,int>
#define pis pair<int,string>
#define psi pair<string,int>
#define pll pair<ll,ll>
template<class S, class T> pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first + t.first, s.second + t.second); }
template<class S, class T> pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first - t.first, s.second - t.second); }
template<class S, class T> ostream& operator<<(ostream& os, pair<S, T> p) { os << "(" << p.first << ", " << p.second << ")"; return os; }
#define X first
#define Y second
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rep1(i,n) for(int i=1;i<=(int)(n);i++)
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;i--)
#define rrep1(i,n) for(int i=(int)(n);i>0;i--)
#define REP(i,a,b) for(int i=a;i<b;i++)
#define in(x, a, b) (a <= x && x < b)
#define all(c) c.begin(),c.end()
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a = b; return 1; } return 0; }
#define UNIQUE(v) v.erase(std::unique(v.begin(), v.end()), v.end());
const ll inf = 1000000001;
const ll INF = (ll)1e18 + 1;
const long double pi = 3.1415926535897932384626433832795028841971L;
#define Sp(p) cout<<setprecision(25)<< fixed<<p<<endl;
// int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
// int dx2[8] = { 1,1,0,-1,-1,-1,0,1 }, dy2[8] = { 0,1,1,1,0,-1,-1,-1 };
vi dx = {1, 0, -1, 0}, dy = {0, 1, 0, -1};
// vi dx2 = { 1,1,0,-1,-1,-1,0,1 }, dy2 = { 0,1,1,1,0,-1,-1,-1 };
#define fio() cin.tie(0); ios::sync_with_stdio(false);
const ll MOD = 1000000007;
// const ll MOD = 998244353;
// #define mp make_pair
//#define endl '\n'

const int N = 212345;
vii G(N);
// vii grundy(N);
// vi grundy2(N, -1);
vector<unordered_map<int, int>> mp(N);
// map<pii, int> mp;
vi first_par(N, -1);
bitset<N> used;

int dfs(int now, int par) {
    if (mp[now].count(par)) return mp[now][par];
    if (first_par[now] == -1) {
        first_par[now] = par;
        vi temp;
        rep (i, G[now].size()) {
            int v = G[now][i];
            if (v == par) continue;
            int res = dfs(v, now);
            temp.push_back(res);
        }
        for (int v: temp) used[v] = true;
        for (int i = 0; i <= N; i++) {
            if (not used[i]) {
                // if (par == -1) grundy2[now] = i;
                // else grundy[now][par_idx] = i;
                mp[now][par] = i;
                for (int v: temp) used[v] = false;
                return i;
            }
        }
    }
    else {
        int x = mp[now][first_par[now]];
        x ^= dfs(first_par[now], now);
        if (par != -1) {
            x ^= dfs(par, now);
        }
        mp[now][par] = x;
        return x;
    }
    return -1; // ダミー
}

signed main() {
    fio();
    
    int n, m;
    cin >> n >> m;
    vi a(m);
    rep (i, m) {
        cin >> a[i];
        a[i]--;
    }

    rep (i, n - 1) {
        int u, v;
        cin >> u >> v;
        u--; v--;
        G[u].push_back(v);
        G[v].push_back(u);
    }
    // rep (i, n) {
    //     grundy[i].resize(G[i].size(), -1);
    // }

    vector<int> gl;
    int x = 0;
    rep (i, m) {
        gl.push_back(dfs(a[i], -1));
        x ^= gl.back();
    }

    if (x == 0) {
        cout << -1 << " " << -1 << endl;
        return 0;
    }

    rep (i, m) {
        int y = gl[i];
        rep (j, G[a[i]].size()) {
            int v = G[a[i]][j];
            // int par_idx = mp[v][a[i]];
            // DEBUG(par_idx);
            // int z = grundy[v][par_idx];
            int z = dfs(v, a[i]);
            if ((x ^ y ^ z) == 0) {
                cout << i + 1 << " " << v + 1 << endl;
                return 0;
            }
        }
    }
}