#include <cstdio>
#include <cstdlib>
#include <vector>
#include <map>
#include <iterator>
#pragma warning(disable:4996) 
#define INF 2140000000
using namespace std;

vector<vector<pair<int, int> > > g;   // to, edgeid
vector<int> parent;              // parent[i]: parent of vertex i
vector<int> val;                 // val[2*i]:val for downward dir, val[2*i+1]: val for upward dir
vector<map<int, int> > z;        // z[i]: vals conter for directed edges from vertex i
vector<int> ans;                 // ans[i]: Grundy number for vertex i

int dfs(int par, int curr)
{
    parent[curr] = par;
    int i;
    for (i = 0; i < (int)g[curr].size(); i++) {
        int next = g[curr][i].first;
        int edge = g[curr][i].second;
        if (next == par) continue;

        int tmp = dfs(curr, next);
        val[edge * 2] = tmp;
        z[curr][tmp]++;
    }
    for (i = 0; i < INF; i++) {
        if (z[curr].empty() || z[curr].find(i) == z[curr].end()) {
            break;
        }
    }
    return i;
}

void dfs2(int par, int curr)
{
    int i;
    for (i = 0; i < (int)g[curr].size(); i++) {
        int next = g[curr][i].first;
        int edge = g[curr][i].second;
        if (next == par) continue;

        int k;
        for (k = 0; k < INF; k++) {
            if (z[curr].empty()) {
                break;
            }
            auto it = z[curr].find(k);
            if (it == z[curr].end()) {
                break;
            }
            int num=it->second;
            if (val[edge*2]==k) num--;
            if (num < 1) {
                break;
            }
        }
        val[edge * 2 + 1] = k;
        z[next][k]++;
        dfs2(curr, next);
    }
    for (i = 0; i < INF; i++) {
        if (z[curr].empty() || z[curr].find(i) == z[curr].end()) {
            break;
        }
    }
    ans[curr] = i;
    return;
}

void solve()
{
    int n, m;
    scanf("%d%d", &n, &m);
    vector<int> a(m);
    int i;
    for (i = 0; i < m; i++) {
        scanf("%d", &a[i]); a[i]--;
    }

    g.resize(n);
    parent.resize(n);
    z.resize(n);
    ans.resize(n);
    val.resize((n-1) * 2);
    for (i = 0; i < n - 1; i++) {
        int p, q;
        scanf("%d%d", &p, &q); p--; q--;
        g[p].push_back(make_pair(q, i));
        g[q].push_back(make_pair(p, i));
    }
    dfs(-1, 0);  
    dfs2(-1, 0);

    int sum = 0;
    for (i = 0; i < m; i++) {
        sum ^= ans[a[i]];
    }
    if (sum == 0) {
        printf("-1 -1\n");
    }
    else {
        int max = -1;
        int maxi = -1;
        for (i = 0; i < m; i++) {
            int tmp = ans[a[i]] & sum;
            if (max < tmp) {
                max = tmp;
                maxi = i;
            }
        }

        int target = ans[a[maxi]]^sum;
        int nextvtx = -1;
        for (i = 0; i < (int)g[a[maxi]].size(); i++) {
            int next = g[a[maxi]][i].first;
            int edge = g[a[maxi]][i].second;
            int tmpval = (next == parent[a[maxi]] ? val[2 * edge + 1] : val[2 * edge]);
            if (target == tmpval) {
                nextvtx = next;
                break;
            }
        }
        printf("%d %d\n", maxi + 1, nextvtx + 1);
    }
    return;
}

int main()
{
    solve();
    return 0;
}