#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "debug.h"
#else
#define dbg(...) 47
#endif
constexpr int N = 1e5;
constexpr long long inf = 1e18;
vector<pair<int, int>> g[N];
int par[N], lvl[N], tin[N], tout[N], up[N];
int timer = 0;
void init(int u, int p) {
tin[u] = timer++;
for (auto [v, w] : g[u]) {
if (v != p) {
up[v] = w;
par[v] = u;
lvl[v] = lvl[u] + 1;
init(v, u);
}
}
tout[u] = timer - 1;
}
long long dp[N];
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n, k, q, e;
cin >> n >> k >> q >> e;
vector<int> a(n - 1), b(n - 1), w(n - 1);
for (int i = 0; i < n - 1; i++) {
cin >> a[i] >> b[i] >> w[i];
a[i]--; b[i]--;
g[a[i]].push_back({b[i], w[i]});
g[b[i]].push_back({a[i], w[i]});
}
for (int i = 0; i < n; i++) {
dp[i] = inf;
}
priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> pq;
for (int i = 0; i < k; i++) {
int s;
cin >> s;
s--;
dp[s] = 0;
pq.push({0, s});
}
while (!pq.empty()) {
auto [k, u] = pq.top();
pq.pop();
if (dp[u] < k) continue;
for (auto [v, w] : g[u]) {
if (k + w < dp[v]) {
dp[v] = k + w;
pq.push({dp[v], v});
}
}
}
e--;
init(e, -1);
while (q--) {
int i, r;
cin >> i >> r;
i--; r--;
int u = a[i], v = b[i];
if (lvl[u] > lvl[v]) {
swap(u, v);
}
if (tin[v] <= tin[r] && tin[r] <= tout[v]) {
long long res = inf, k = 0;
while (r != v) {
res = min(res, dp[r] + k);
if (res == 0) {
break;
}
k += up[r];
r = par[r];
}
if (res == inf) {
cout << "oo\n";
} else {
cout << res << '\n';
}
} else {
cout << "escaped\n";
}
}
return 0;
}
