#include <bits/stdc++.h>
#define ford(i,x,y) for(int i=x;i<=y;++i)
#define forr(i,x,y) for(int i=x;i>=y;--i)
#define ll long long
#define ld long double
#define isz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define pb push_back
using namespace std;
const int N=1e5+10;
int n, q, deg[N];
vector <int> G[N<<1];
void sub1(){
int leaf=0;
ford (i, 1, n)
if (deg[i]==1)++leaf;
int d; cin>>d;
vector <int> uv(d), cnt(n+1, 0);
ford (i, 0, d-1){
cin>>uv[i];
++leaf;
if (!cnt[uv[i]])--leaf;
++cnt[uv[i]];
}
if (leaf&1){
cout<<-1;
return;
}
int cnt1=0, cnt2=0;
ll ans=0;
ford (i, 2, n){
if (cnt[i]>2){
int k=(cnt[i]-1)/2;
cnt[i]-=k*2;
ans+=k*2;
}
if (!cnt[i])++cnt1;
else cnt2+=cnt[i];
}
int mn=min(cnt1, cnt2);
ans+=3*mn;
cnt1-=mn;
cnt2-=mn;
ans+=cnt1;
ans+=cnt2*2;
cout<<ans;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin>>n>>q;
ford (i, 2, n){
int u, v;
cin>>u>>v;
G[u].pb(v);
G[v].pb(u);
++deg[u];
++deg[v];
}
sub1();
return 0;
}
