#include<bits/stdc++.h>
using namespace std;
#define int long long
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
#define bp __builtin_popcount
#define ll long long
#define mp make_pair
#define f first
#define s second
#define Time (double)clock()/CLOCKS_PER_SEC
const int N = 2e5 + 7;
vector <int> g[N];
ii ed[N];
set <ii> ms[N];
int l[N], num[N], par[N];
bool us[N];
int n, m, q;
void dfs(int u, int p) {
par[u] = p;
for (int v : g[u])
if (v != p)
dfs(v, u);
}
int ans = 0;
void solve(int u, int p, int x) {
++ans;
for (int v : g[u])
if (v != p) {
auto t = ms[v].lower_bound(mp(x + 1, -1));
if (t == ms[v].begin())
continue;
--t;
solve(v, u, min(x, t->s));
}
}
signed main() {
#ifdef HOME
freopen("input.txt", "r", stdin);
#else
ios_base::sync_with_stdio(0); cin.tie(0);
#endif
cin >> n >> m >> q;
for (int i = 0; i < n - 1; ++i) {
int u, v;
cin >> u >> v;
ed[i] = mp(u, v);
g[u].app(v); g[v].app(u);
}
for (int i = 0; i < m; ++i) {
cin >> num[i];
--num[i];
}
int root;
cin >> root;
dfs(root, root);
for (int i = 0; i < m; ++i) {
int u = ed[num[i]].f, p = ed[num[i]].s;
if (u == par[p])
swap(u, p);
if (us[num[i]]) {
//cout << "insert " << u << " : " << l[num[i]] << ' ' << i << '\n';
ms[u].insert(mp(l[num[i]], i));
}
else {
l[num[i]] = i;
}
us[num[i]] ^= 1;
}
for (int i = 0; i < n - 1; ++i) {
if (us[i]) {
int u = ed[i].f, p = ed[i].s;
if (u == par[p])
swap(u, p);
//cout << "insert " << u << " : " << l[i] << ' ' << m << '\n';
ms[u].insert(mp(l[i], m));
}
}
solve(root, root, N);
cout << ans << '\n';
}
