#include <bits/stdc++.h>
#define L(i, j, k) for(int i = (j); i <= (k); i++)
#define R(i, j, k) for(int i = (j); i >= (k); i--)
#define ll long long
#define sz(a) ((int) a.size())
#define all(a) a.begin(), a.end()
#define vi vector<int>
#define pb emplace_back
#define me(a, x) memset(a, x, sizeof(a))
#define fst first
#define snd second
#define ii pair<int,int>
using namespace std;
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n,q;cin>>n>>q;
L(i,0,n-1){
int u,v;cin>>u>>v;
}
int leaf_cnt=2;
int d;cin>>d;
vi p(d);
L(i,0,d-1){
cin>>p[i];
leaf_cnt++;
}
if(leaf_cnt%2){cout<<-1<<endl;return 0;}
sort(all(p));
int ans=n-1;
for(int i=1;i<d;i+=2){
ans+=(p[i]-p[i-1])+2;
}
cout<<ans<<endl;
}
