//#include <bits/stdc++.h>
#include "bits/stdc++.h"
using namespace std;
typedef long long ll;

/*
#include "boost/multiprecision/cpp_int.hpp"
#include "boost/multiprecision/cpp_dec_float.hpp"
namespace mp = boost::multiprecision;
typedef mp::cpp_int LL;
typedef mp::number<mp::cpp_dec_float<1024>> DD;// 仮数部が1024ビットの浮動小数点数型(TLEしたら小さくする)
*/
 
typedef long double dd;
#define i_7 (ll)(1E9+7)
//#define i_7 998244353
#define i_5 i_7-2
ll mod(ll a){
    ll c=a%i_7;
    if(c>=0)return c;
    return c+i_7;
}
typedef pair<ll,ll> l_l;
typedef pair<dd,dd> d_d;
ll inf=(ll)1E16;
#define rep(i,l,r) for(ll i=l;i<=r;i++)
#define rrep(i,r,l) for(ll i=r;i>=l;i--)
#define pb push_back
ll max(ll a,ll b){if(a<b)return b;else return a;}
ll min(ll a,ll b){if(a>b)return b;else return a;}
void Max(ll &pos,ll val){pos=max(pos,val);}//Max(dp[n],dp[n-1]);
void Min(ll &pos,ll val){pos=min(pos,val);}
void Add(ll &pos,ll val){pos=mod(pos+val);}
dd EPS=1E-9;
#define fastio ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define fi first
#define se second
//#define endl "\n"  //インタラクティブで消す！！！！！！！！！！！！！！！！！！！！！
#define SORT(v) sort(v.begin(),v.end())
#define ERASE(v) v.erase(unique(v.begin(),v.end()),v.end())
#define POSL(v,x) (lower_bound(v.begin(),v.end(),x)-v.begin())
#define POSU(v,x) (upper_bound(v.begin(),v.end(),x)-v.begin())
template<class T,class S>
inline bool chmax(T &a, S b) {
    if(a < b) {
        a = b;
        return true;
    }
    return false;
}
template<class T,class S>
inline bool chmin(T &a, S b) {
    if(a > b) {
        a = b;
        return true;
    }
    return false;
}

void mod_print(ll k){
    ll P=50000;
    rep(y,1,P){
        ll x=mod(y*k);
        
        if(abs(x)<=P||x+P>=i_7){
            if(x+P>=i_7){
                x-=i_7;
            }
            cout<<x<<"/"<<y<<endl;
            //cout<<setprecision(5)<<(dd)x/(dd)y;
            return;
        }
    }
    cout<<"nun"<<endl;
}
#define all(c) c.begin(),c.end()
typedef vector<ll> vl;
//////////////////////////

#define N 200005
ll n,m;
vector<ll>v[N];
ll g[N];

void dfs1(ll id,ll par){
    set<ll>s;
    for(auto x:v[id]){
        if(x==par)continue;
        dfs1(x,id);
        s.insert(g[x]);
    }
    rep(z,0,N){
        if(s.find(z)==s.end()){
            g[id]=z;
            return;
        }
    }
}
void dfs2(ll id,ll par,ll val){
    map<ll,ll>s;
    s[val]++;
    for(auto x:v[id]){
        if(x==par)continue;
        s[g[x]]++;
    }
    rep(z,0,N){
        if(s[z]==0){
            g[id]=z;
            break;
        }
    }
    for(auto x:v[id]){
        if(x==par)continue;
        if(s[g[x]]==1){
            dfs2(x,id,g[x]);
        }else{
            dfs2(x,id,g[id]);
        }
    }
}

int main(){fastio
    cin>>n>>m;
    ll a[m];rep(i,0,m-1)cin>>a[i];
    rep(i,1,n-1){
        ll b,c;cin>>b>>c;
        v[b].pb(c);
        v[c].pb(b);
    }
    dfs1(1,0);
    dfs2(1,0,inf);
  //  rep(i,1,n)cout<<g[i]<<" ";cout<<endl;
    ll G=0;
    rep(i,0,m-1){
        G^=g[a[i]];
    }
    if(G==0){
        cout<<-1<<" "<<-1<<endl;
        return 0;
    }
    rep(i,0,m-1){
        rrep(z,22,0){
            if((G>>z)&1){
                if((g[a[i]]>>z)&1){
                    ll pos=a[i];
                    dfs1(pos,0);
                    ll R=G^g[a[i]];
                    for(auto x:v[pos]){
                        if(g[x]==R){
                            cout<<i+1<<" "<<x<<endl;
                            return 0;
                        }
                    }
                }else{
                    break;
                }
            }
        }
    }
    
    return 0;
}