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

using Int = long long;
const char newl = '\n';

template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}
template<typename T> void drop(const T &x){cout<<x<<endl;exit(0);}
template<typename T=int>
vector<T> read(size_t n){
  vector<T> ts(n);
  for(size_t i=0;i<n;i++) cin>>ts[i];
  return ts;
}


template<typename F>
struct FixPoint : F{
  FixPoint(F&& f):F(forward<F>(f)){}
  template<typename... Args>
  decltype(auto) operator()(Args&&... args) const{
    return F::operator()(*this,forward<Args>(args)...);
  }
};
template<typename F>
inline decltype(auto) MFP(F&& f){
  return FixPoint<F>{forward<F>(f)};
}

//INSERT ABOVE HERE
signed main(){
  cin.tie(0);
  ios::sync_with_stdio(0);

  int n,m;
  cin>>n>>m;
  auto as=read(m);
  for(int &a:as) a--;

  vector<vector<int>> G(n);
  for(int i=1;i<n;i++){
    int u,v;
    cin>>u>>v;
    u--;v--;
    G[u].emplace_back(v);
    G[v].emplace_back(u);
  }

  using P = pair<int, int>;
  map<P, int> dp;
  auto func=
    MFP([&](auto dfs,int v,int p)->int{
      if(dp.count(P(v,p))) return dp[P(v,p)];
      int &res=dp[P(v,p)];
      res=0;
      set<int> ss;
      for(int u:G[v]){
        if(u==p) continue;
        ss.emplace(dfs(u,v));
      }
      while(ss.count(res)) res++;
      return res;
    });

  for(int i=0;i<n;i++) func(i,-1);

  int ans=0;
  for(int a:as) ans^=func(a,-1);
  if(ans==0) drop("-1 -1");

  for(int i=0;i<m;i++){
    int a=as[i];
    for(int b:G[a]){
      if(ans^func(a,-1)^func(b,a)) continue;
      cout<<i+1<<' '<<b+1<<endl;
      return 0;
    }
  }
  abort();
  return 0;
}