#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)
#define rep2(i, x, n) for (int i = x; i <= n; i++)
#define rep3(i, x, n) for (int i = x; i >= n; i--)
#define each(e, v) for (auto &e : v)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;

template <typename T>
bool chmax(T &x, const T &y) {
    return (x < y) ? (x = y, true) : false;
}

template <typename T>
bool chmin(T &x, const T &y) {
    return (x > y) ? (x = y, true) : false;
}

template <typename T>
int flg(T x, int i) {
    return (x >> i) & 1;
}

template <typename T>
void print(const vector<T> &v, T x = 0) {
    int n = v.size();
    for (int i = 0; i < n; i++) cout << v[i] + x << (i == n - 1 ? '\n' : ' ');
    if (v.empty()) cout << '\n';
}

template <typename T>
void printn(const vector<T> &v, T x = 0) {
    int n = v.size();
    for (int i = 0; i < n; i++) cout << v[i] + x << '\n';
}

template <typename T>
int lb(const vector<T> &v, T x) {
    return lower_bound(begin(v), end(v), x) - begin(v);
}

template <typename T>
int ub(const vector<T> &v, T x) {
    return upper_bound(begin(v), end(v), x) - begin(v);
}

template <typename T>
void rearrange(vector<T> &v) {
    sort(begin(v), end(v));
    v.erase(unique(begin(v), end(v)), end(v));
}

template <typename T>
vector<int> id_sort(const vector<T> &v, bool greater = false) {
    int n = v.size();
    vector<int> ret(n);
    iota(begin(ret), end(ret), 0);
    sort(begin(ret), end(ret), [&](int i, int j) { return greater ? v[i] > v[j] : v[i] < v[j]; });
    return ret;
}

template <typename S, typename T>
pair<S, T> operator+(const pair<S, T> &p, const pair<S, T> &q) {
    return make_pair(p.first + q.first, p.second + q.second);
}

template <typename S, typename T>
pair<S, T> operator-(const pair<S, T> &p, const pair<S, T> &q) {
    return make_pair(p.first - q.first, p.second - q.second);
}

template <typename S, typename T>
istream &operator>>(istream &is, pair<S, T> &p) {
    S a;
    T b;
    is >> a >> b;
    p = make_pair(a, b);
    return is;
}

template <typename S, typename T>
ostream &operator<<(ostream &os, const pair<S, T> &p) {
    return os << p.first << ' ' << p.second;
}

struct io_setup {
    io_setup() {
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout << fixed << setprecision(15);
    }
} io_setup;

const int inf = (1 << 30) - 1;
const ll INF = (1LL << 60) - 1;
const int MOD = 1000000007;
// const int MOD = 998244353;

template <bool directed = false>
struct Graph {
    struct edge {
        int to, id;
        int grundy;
        edge(int to, int id) : to(to), id(id) {}
    };

    vector<vector<edge>> es;
    const int n;
    int m;

    vector<vector<int>> cnt;
    vector<int> g1, g2;

    Graph(int n) : es(n), n(n), m(0), cnt(n), g1(n), g2(n) {}

    void add_edge(int from, int to) {
        es[from].emplace_back(to, m);
        if (!directed) es[to].emplace_back(from, m);
        m++;
    }

    int dfs1(int now, int pre) {
        int d = sz(es[now]);
        cnt[now].assign(d + 1, 0);
        each(e, es[now]) {
            if (e.to == pre) continue;
            int g = dfs1(e.to, now);
            e.grundy = g;
            if (g <= d) cnt[now][g]++;
        }
        rep(i, d + 1) {
            if (cnt[now][i] == 0) return g1[now] = i;
        }
        return g1[now] = d + 1;
    }

    void dfs2(int now, int pre, int top) {
        int d = sz(es[now]);
        if (pre != -1 && top <= d) cnt[now][top]++;
        rep(i, d + 1) {
            if (cnt[now][i] == 0) g2[now] = i;
        }
        each(e, es[now]) {
            if (e.to == pre) {
                e.grundy = top;
            } else {
                int x = g2[now];
                if (cnt[now][g1[e.to]] == 1) chmin(x, g1[e.to]);
                dfs2(e.to, now, x);
            }
        }
    }

    void solve(const vector<int> &a) {
        dfs1(0, -1);
        dfs2(0, -1, inf);
        // print(g1), print(g2);
        int XOR = 0;
        each(e, a) XOR ^= g2[e];
        if (XOR == 0) {
            cout << -1 << ' ' << -1 << '\n';
            return;
        }
        rep(i, sz(a)) {
            int e = a[i];
            int t = g2[e] ^ XOR;
            // cout << e + 1 << ' ' << t << '\n';
            if (g2[e] > t) {
                each(u, es[e]) {
                    if (u.grundy == t) {
                        cout << i + 1 << ' ' << u.to + 1 << '\n';
                        return;
                    }
                }
            }
        }
    }
};

int main() {
    int N, M;
    cin >> N >> M;

    vector<int> a(M);
    rep(i, M) {
        cin >> a[i];
        a[i]--;
    }

    Graph G(N);
    rep(i, N - 1) {
        int u, v;
        cin >> u >> v;
        u--, v--;
        G.add_edge(u, v);
    }

    G.solve(a);
}