#include <bits/stdc++.h>
//ako ovaj vaso daso misli da me pobedjuje.....
using namespace std;
#define int long long
#define f first
#define s second
const int N = 1e5 + 69;
const int K = 18;
const int inf = 1e18;
int up[N][K];
int n, s, q, e, cnt[N], dep[N], par[N];
int tin[N], tout[N], timer, cost[N];
vector<int> shop;
vector<pair<int, int>> g[N];
vector<tuple<int, int, int>> edges;
bool anc(int a, int b) {
return tin[a] <= tin[b] && tout[a] >= tout[b];
}
int Lca(int a, int b) {
if (anc(a, b))
return a;
else if (anc(b, a))
return b;
for (int i = K - 1;i >= 0;i--) {
if (!anc(up[a][i], b) && up[a][i] > 0)
a = up[a][i];
}
return up[a][0];
}
int distance(int a, int b) {
return dep[a] + dep[b] - 2 * dep[Lca(a, b)];
}
void dfs(int v, int p) {
tin[v] = ++timer;
par[v] = p;
up[v][0] = p;
for (int i = 1;i < K;i++)
up[v][i] = up[up[v][i - 1]][i - 1];
for (auto u : g[v]) {
if (u.f == p)
continue;
dep[u.f] = dep[v] + u.s;
dfs(u.f, v);
}
tout[v] = timer;
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int tt = 1;
//cin >> tt;
while (tt--) {
cin >> n >> s >> q >> e;
for (int i = 1;i <= n - 1;i++) {
int a, b, w;
cin >> a >> b >> w;
g[a].push_back({b, w});
g[b].push_back({a, w});
edges.push_back({a, b, w});
}
dfs(1, 0);
for (int i = 1;i <= s;i++) {
int x;
cin >> x;
cnt[x] = 1;
shop.push_back(x);
}
for (int j = 0;j < q;j++) {
int i, st;
cin >> i >> st;
--i;
int x, a, b, w;
tie(a, b, w) = edges[i];
x = (dep[a] > dep[b] ? a : b);
int ans = inf;
if (s == n) {
if (anc(x, e) && anc(x, st))
ans = -1;
else if (!anc(x, e) && !anc(x, st))
ans = -1;
else
ans = 0;
}
else {
if (anc(x, e) && anc(x, st))
ans = -1;
else if (!anc(x, e) && !anc(x, st))
ans = -1;
else {
for (auto u : shop) {
if ((!anc(x, u) && !anc(x, st)) || (anc(x, u) && anc(x, st)))
ans = min(ans, distance(u, st));
}
}
}
if (ans == inf)
cout << "oo\n";
else if (ans == -1)
cout << "escaped\n";
else
cout << ans << '\n';
}
}
return 0;
}
