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

using ll = long long;
using pii = pair<int, int>;
template <class T>
using V = vector<T>;
template <class T>
using VV = V<V<T>>;

#define pb push_back
#define eb emplace_back
#define mp make_pair
#define fi first
#define se second
#define rep(i, n) rep2(i, 0, n)
#define rep2(i, m, n) for (int i = m; i < (n); i++)
#define per(i, b) per2(i, 0, b)
#define per2(i, a, b) for (int i = int(b) - 1; i >= int(a); i--)
#define ALL(c) (c).begin(), (c).end()
#define SZ(x) ((int)(x).size())

constexpr ll TEN(int n) { return (n == 0) ? 1 : 10 * TEN(n - 1); }

template <class T, class U>
void chmin(T& t, const U& u) {
    if (t > u) t = u;
}
template <class T, class U>
void chmax(T& t, const U& u) {
    if (t < u) t = u;
}

template <class T, class U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
    os << "(" << p.first << "," << p.second << ")";
    return os;
}

template <class T>
ostream& operator<<(ostream& os, const vector<T>& v) {
    os << "{";
    rep(i, v.size()) {
        if (i) os << ",";
        os << v[i];
    }
    os << "}";
    return os;
}

#ifdef LOCAL
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << " " << H;
    debug_out(T...);
}
#define debug(...) \
    cerr << __LINE__ << " [" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define dump(x) cerr << __LINE__ << " " << #x << " = " << (x) << endl
#else
#define debug(...) (void(0))
#define dump(x) (void(0))
#endif

VV<int> _g, g;
V<int> dgr, gr;
VV<int> cnt;

void dfs(int v, int p) {
    for (int to : _g[v]) {
        if (to != p) {
            dfs(to, v);
            g[v].pb(to);
        }
    }

    cnt[v].resize(g[v].size() + 5);
    for (int to : g[v]) cnt[v][dgr[to]]++;
    dgr[v] = 0;
    while (cnt[v][dgr[v]]) dgr[v]++;
}

V<map<int, int>> toc;

void calc(int v, int px) {
    gr[v] = dgr[v];
    if (px < cnt[v].size()) cnt[v][px]++;
    while (cnt[v][gr[v]]) gr[v]++;

    for (int to : g[v]) {
        int nx = gr[v];
        if (dgr[to] < gr[v] && cnt[v][dgr[to]] == 1) {
            nx = dgr[to];
        }
        toc[v][to] = nx;
        calc(to, nx);
    }
}

int main() {
    int N, M;
    cin >> N >> M;
    V<int> A(M);
    rep(i, M) cin >> A[i], --A[i];
    _g.resize(N);
    g.resize(N);
    gr.resize(N);
    dgr.resize(N);
    cnt.resize(N);
    toc.resize(N);

    rep(i, N - 1) {
        int a, b;
        cin >> a >> b;
        --a, --b;
        _g[a].pb(b);
        _g[b].pb(a);
    }
    dfs(0, -1);
    calc(0, -1);

    int xo = 0;
    for (int v : A) xo ^= gr[v];
    debug(dgr, gr, xo);

    if (xo == 0) {
        cout << "-1 -1" << endl;
    } else {
        V<bool> vis(N);
        rep(i, M) {
            int v = A[i];
            if (vis[v]) continue;
            vis[v] = 1;
            for (int to : _g[v]) {
                if (toc[v].count(to)) {
                    if ((xo ^ gr[v] ^ dgr[to]) == 0) {
                        cout << i + 1 << ' ' << to + 1 << endl;
                        return 0;
                    }
                } else {
                    if ((xo ^ gr[v] ^ toc[to][v]) == 0) {
                        cout << i + 1 << ' ' << to + 1 << endl;
                        return 0;
                    }
                }
            }
        }
    }
    return 0;
}