#include <bits/stdc++.h>
#define file_io freopen("input.txt", "r", stdin);freopen("output.txt", "w", stdout);
#define fast_io ios::sync_with_stdio(false);cin.tie(0);
#define what(x) cerr << #x << " is " << x << endl;
#define kill(x) {cout << x << '\n'; continue;}
#define all(x) (x).begin(), (x).end()
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pb push_back
#define ll long long
#define F first
#define S second
const ll inf = 1e14, mod = 1e9 + 7, delta = 1e8, SQ = 800; //998244353
using namespace std;
const ll N = 1e3 + 10, LG = 20;
#define piii array<int, 3>
vector<piii> adj[N];
vector<int> maghaze;
bitset<N> mark;
ll dis[N];
void dfs (int v, int e) {
mark[v] = true;
for (auto u: adj[v])
if (u[2] != e && !mark[u[0]])
dfs(u[0], e);
}
int32_t main() {
fast_io;
int n, s, q, e;
cin >> n >> s >> q >> e;
for (int i = 1; i < n; i++) {
int u, v, w;
cin >> u >> v >> w;
adj[u].pb({v, w, i});
adj[v].pb({u, w, i});
}
for (int i = 1; i <= s; i++) {
int v;
cin >> v;
maghaze.pb(v);
}
while (q--) {
int ii, r;
cin >> ii >> r;
mark.reset();
dfs(r, ii);
if (mark[e]) kill("escaped");
mark.reset();
priority_queue<pii, vector<pii>, greater<pii>> q;
q.push(pii(0, r));
memset(dis, 63, sizeof dis);
dis[r] = 0;
while (q.size()) {
int v = q.top().S;
q.pop();
if (mark[v]) continue;
mark[v] = true;
for (auto u: adj[v]) {
if (u[2] != ii && dis[u[0]] > dis[v] + u[1]) {
dis[u[0]] = dis[v] + u[1];
q.push(pii(dis[u[0]], u[0]));
}
}
}
ll mn = inf;
for (auto u: maghaze) mn = min(mn, dis[u]);
if (mn == inf) cout << "oo\n";
else cout << mn << '\n';
}
return 0;
}
