#include <bits/stdc++.h>
using namespace std;
using lint = long long;
using pint = pair<int, int>;
using plint = pair<lint, lint>;
struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
#define ALL(x) (x).begin(), (x).end()
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
template <typename T> void ndarray(vector<T> &vec, int len) { vec.resize(len); }
template <typename T, typename... Args> void ndarray(vector<T> &vec, int len, Args... args) { vec.resize(len); for (auto &v : vec) ndarray(v, args...); }
template <typename V, typename T> void ndfill(V &x, const T &val) { x = val; }
template <typename V, typename T> void ndfill(vector<V> &vec, const T &val) { for (auto &v : vec) ndfill(v, val); }
template <typename T> bool chmax(T &m, const T q) { if (m < q) {m = q; return true;} else return false; }
template <typename T> bool chmin(T &m, const T q) { if (m > q) {m = q; return true;} else return false; }
template <typename T1, typename T2> pair<T1, T2> operator+(const pair<T1, T2> &l, const pair<T1, T2> &r) { return make_pair(l.first + r.first, l.second + r.second); }
template <typename T1, typename T2> pair<T1, T2> operator-(const pair<T1, T2> &l, const pair<T1, T2> &r) { return make_pair(l.first - r.first, l.second - r.second); }
template <typename T> vector<T> srtunq(vector<T> vec) { sort(vec.begin(), vec.end()), vec.erase(unique(vec.begin(), vec.end()), vec.end()); return vec; }
template <typename T> istream &operator>>(istream &is, vector<T> &vec) { for (auto &v : vec) is >> v; return is; }
template <typename... T> istream &operator>>(istream &is, tuple<T...> &tpl) { std::apply([&is](auto &&... args) { ((is >> args), ...);}, tpl); return is; }
template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec) { os << '['; for (auto v : vec) os << v << ','; os << ']'; return os; }
template <typename... T> ostream &operator<<(ostream &os, const tuple<T...> &tpl) { std::apply([&os](auto &&... args) { ((os << args << ','), ...);}, tpl); return os; }
template <typename T> ostream &operator<<(ostream &os, const deque<T> &vec) { os << "deq["; for (auto v : vec) os << v << ','; os << ']'; return os; }
template <typename T> ostream &operator<<(ostream &os, const set<T> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <typename T> ostream &operator<<(ostream &os, const multiset<T> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &pa) { os << '(' << pa.first << ',' << pa.second << ')'; return os; }
template <typename TK, typename TV> ostream &operator<<(ostream &os, const map<TK, TV> &mp) { os << '{'; for (auto v : mp) os << v.first << "=>" << v.second << ','; os << '}'; return os; }
template <typename TK, typename TV> ostream &operator<<(ostream &os, const unordered_map<TK, TV> &mp) { os << '{'; for (auto v : mp) os << v.first << "=>" << v.second << ','; os << '}'; return os; }
#ifdef HITONANODE_LOCAL
#define dbg(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ") " << __FILE__ << endl
#else
#define dbg(x)
#endif

int mex(vector<int> v)
{
    sort(v.begin(), v.end());
    int ret = 0;
    for (auto x : v)
    {
        if (x == ret) ret++;
        if (x > ret) break;
    }
    return ret;
}

struct rand_int_
{
    using lint = long long;
    mt19937 mt;
    rand_int_() : mt(chrono::steady_clock::now().time_since_epoch().count()) {}
    lint operator()(lint x) { return this->operator()(0, x); } // [0, x)
    lint operator()(lint l, lint r)
    {
        uniform_int_distribution<lint> d(l, r - 1);
        return d(mt);
    }
} rnd;

int main()
{
    int N, M;
    cin >> N >> M;
    vector<int> A(M);
    cin >> A;
    for (auto &a : A) a--;
    vector<vector<int>> to(N);

    int root = rnd(N);
    REP(_, N - 1)
    {
        int u, v;
        cin >> u >> v;
        u--, v--;
        to[u].emplace_back(v);
        to[v].emplace_back(u);
    }
    vector<int> gchild(N), gpar(N, 1e9), grundy(N), par(N, -1);

    auto gdfs = [&](auto &&gdfs, int now, int prv) -> void {
        vector<int> gs;
        for (auto nxt : to[now]) if (nxt != prv)
        {
            par[nxt] = now;
            gdfs(gdfs, nxt, now);
            gs.emplace_back(gchild[nxt]);
        }
        gchild[now] = mex(gs);
    };
    gdfs(gdfs, root, -1);

    auto pardfs = [&](auto &&pardfs, int now, int prv) -> void {
        int D = to[now].size();
        vector<int> cnt(D + 1);
        cnt[min(D, gpar[now])]++;
        for (auto nxt : to[now]) if (nxt != prv)
        {
            int g = min(D, gchild[nxt]);
            cnt[g]++;
        }
        set<int> ok;
        REP(i, cnt.size()) if (!cnt[i]) ok.insert(i);
        grundy[now] = *ok.begin();
        for (auto nxt : to[now]) if (nxt != prv)
        {
            int g = min(D, gchild[nxt]);
            cnt[g]--;
            if (!cnt[g]) ok.insert(g);
            gpar[nxt] = *ok.begin();
            cnt[g]++;
            ok.erase(g);
        }
        for (auto nxt : to[now]) if (nxt != prv) pardfs(pardfs, nxt, now);
    };
    pardfs(pardfs, root, -1);

    dbg(gchild);
    dbg(gpar);
    dbg(grundy);

    int XOR = 0;
    for (auto a : A)
    {
        XOR ^= grundy[a - 1];
    }
    if (XOR)
    {
        vector<int> checked(N);
        REP(i, A.size())
        {
            int r = A[i];
            if (checked[r]) continue;
            checked[r] = 1;
            for (auto s : to[r])
            {
                if (par[r] == s and (grundy[r] ^ gpar[r]) == XOR)
                {
                    cout << i + 1 << ' ' << s + 1 << '\n';
                    return 0;
                }
                if (par[r] != s and (grundy[r] ^ gchild[s]) == XOR)
                {
                    cout << i + 1 << ' ' << s + 1 << '\n';
                    return 0;
                }
            }
        }
    }
    else puts("-1 -1");
}