#include <bits/stdc++.h>
using namespace std;
#define all(x) x.begin(), x.end()
const int mxN = 10005;
vector<pair<int, int>> adj[mxN];
set<int> en_time[mxN], st_time[mxN];
int ans = 0;
void dfs(int u = 1, int par = 0, int tim = mxN){
ans += 1;
for(auto [v, t] : adj[u]){
if(v == par) continue;
if((int) st_time[t].size() == 0) continue;
if((int) *st_time[t].begin() > tim) continue;
auto lb = en_time[t].lower_bound(tim);
if(lb == en_time[t].end()) --lb;
dfs(v, u, min(*lb, tim));
}
}
signed main(){
ios::sync_with_stdio(0);
cin.tie(nullptr); cout.tie(nullptr);
int n, m, q;
cin >> n >> m >> q;
vector<int> on(n + 5, 0);
for(int i = 0, u, v; i < n - 1; ++i){
cin >> u >> v;
adj[u].push_back({v, i + 1});
adj[v].push_back({u, i + 1});
}
for(int i = 0, x; i < m; ++i){
cin >> x;
on[x] ^= 1;
if(on[x]){
st_time[x].insert(i);
}else{
en_time[x].insert(i);
}
}
for(int i = 0; i < n; ++i){
if((int) en_time[i + 1].size() == 0){
en_time[i + 1].insert(mxN);
}
}
int x;
cin >> x;
dfs(x);
cout << ans << "\n";
return 0;
}
