#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<complex>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<utility>
#include<tuple>
using namespace std;
typedef long long ll;
typedef unsigned int ui;
const ll mod = 1000000007;
const ll INF = (ll)1000000007 * 1000000007;
typedef pair<int, int> P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define Per(i,sta,n) for(int i=n-1;i>=sta;i--)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
typedef long double ld;
const ld eps = 1e-8;
const ld pi = acos(-1.0);
typedef pair<ll, ll> LP;
int dx[4]={1,-1,0,0};
int dy[4]={0,0,1,-1};

int n,m;
int a[200010];
map<P,int> grundy;
vector<int> G[200010];

int dfs(int s,int par){
    if(grundy[P(s,par)]) return grundy[P(s,par)]-1;
    set<int> v={};
    for(int t:G[s]){
        if(t==par) continue;
        v.insert(dfs(t,s));
    }
    if(v.empty()) {
        grundy[P(s,par)]=1;
        return 0;
    }
    auto it=v.begin();int id=0;
    while(*it==id){
        it++;id++;
        if(it==v.end()) {
            grundy[P(s,par)]=id+1;
            return id;
        }
    }
    grundy[P(s,par)]=id+1;
    return id;
}

void solve(){
    cin >> n >> 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);
    }
    int x=0,ma=-1,ma_id;
    rep(i,m){
        int s=dfs(a[i],-1);
        x^=s;
        if(ma<s){
            ma=s;
            ma_id=i;
        }
    }
    if(x==0){
        cout << -1 << " " << -1 << endl;
    }
    else{
        for(int s:G[a[ma_id]]){
            if(dfs(s,a[ma_id])==(x^ma)){
                cout << ma_id+1 << " " << s+1 << endl;
            }
        }
    }
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(50);
    solve();
}