#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N = 1e5 + 10;
const ll inf = 1e18;
int n, m, q, rt, s[N], gs[N] = { 0 };
vector<pair<int, int>> gr[N];
pair<int, int> edges[N];
set<int> nd[N];
map<int, ll> ans[N];
struct graph {
vector<vector<int>> adj;
int n;
graph() {}
graph(int _n) : n(_n) {
adj.resize(n);
}
inline void add(int x, int y) {
adj[x].push_back(y);
adj[y].push_back(x);
}
};
struct lca_graph : graph {
using graph::adj;
using graph::n;
vector<vector<int>> par;
vector<int> lev, path;
int lv = 0, lg;
lca_graph(int _n) : graph(_n) {
lg = __lg(n) + 1;
par = vector<vector<int>>(n, vector<int>(lg, -1));
lev = vector<int>(n, 0);
}
void make_lca(int x, int p) {
path.push_back(x);
lv++;
lev[x] = lv;
for (int i = 0; (1<<i) < path.size(); ++i) {
par[x][i] = path[path.size()-1-(1<<i)];
}
for (auto u: adj[x]) {
if (u != p) {
make_lca(u, x);
}
}
lv--;
path.pop_back();
}
int ka(int u, int k) {
if (k > lev[u] - 1) return 0;
while (k > 0) {
int clg = (int) __lg(k);
k -= pow(2, lg);
u = par[u][clg];
}
return u;
}
int lca(int u, int v) {
int du = lev[u], dv = lev[v];
if (du < dv) {
v = ka(v, dv-du);
dv = du;
} else if (du > dv) {
u = ka(u, du-dv);
du = dv;
}
if (u == v) return u;
for (int i = lg-1; i >= 0; --i) {
if (par[u][i] != par[v][i]) {
u = par[u][i];
v = par[v][i];
}
}
return par[u][0];
}
};
lca_graph g(1);
ll dst[N];
void dfs_st(int x, int p) {
dst[x] = inf;
if (gs[x]) dst[x] = 0;
for (auto [u, w]: gr[x]) {
if (u == p) continue;
dfs_st(u, x);
dst[x] = min(dst[x], dst[u] + (ll) w);
}
}
ll tree[262144] = { inf }, lazy[262144] = { 0 };
void push(int L, int R, int id) {
tree[id] += lazy[id];
if (L != R) for (int i = 0; i < 2; ++i) lazy[2 * id + i] += lazy[id];
lazy[id] = 0;
}
void pull(int id) { tree[id] = min(tree[2 * id], tree[2 * id + 1]); }
void ch(int x, ll y, int L = 0, int R = 131072 - 1, int id = 1) {
push(L, R, id); if (x < L || R < x) return;
if (L == x && x == R) { tree[id] = y; return; }
int M = (L+R)/2; ch(x, y, L, M, 2 * id);
ch(x, y, M + 1, R, 2 * id + 1); pull(id);
}
void add(int l, int r, ll v, int L = 0, int R = 131072 - 1, int id = 1) {
push(L, R, id); if (r < L || R < l) return;
if (l <= L && R <= r) { lazy[id] = v; push(L, R, id); return; }
int M = (L+R)/2; add(l, r, v, L, M, 2 * id);
add(l, r, v, M + 1, R, 2 * id + 1); pull(id);
}
ll get(int l, int r, int L = 0, int R = 131072 - 1, int id = 1) {
push(L, R, id); if (r < L || R < l) return inf;
if (l <= L && R <= r) return tree[id];
int M = (L+R)/2;
return min(get(l, r, L, M, 2 * id), get(l, r, M + 1, R, 2 * id + 1));
}
int csz = 0;
void dfs_ans(int x, int p) {
ch(csz, dst[x]);
for (auto u: nd[x]) {
int ld = g.lev[x] - g.lev[u];
ans[x][u] = get(csz - ld, csz);
}
csz++;
for (auto [u, w]: gr[x]) {
if (u == p) continue;
add(0, csz, (ll)w);
dfs_ans(u, x);
add(0, csz, (ll)-w);
}
csz--;
ch(csz, inf);
}
int main() {
cin >> n >> m >> q >> rt;
g = lca_graph(n);
for (int i = 0; i < n - 1; ++i) {
int x, y, w;
cin >> x >> y >> w;
edges[i] = make_pair(--x, --y);
g.add(x, y);
gr[x].push_back({y, w});
gr[y].push_back({x, w});
}
for (int i = 0; i < m; ++i) {
cin >> s[i];
gs[--s[i]] = 1;
}
g.make_lca(--rt, -1);
int qi[q], qs[q];
for (int i = 0; i < q; ++i) {
cin >> qi[i] >> qs[i];
qi[i]--; qs[i]--;
int x = edges[qi[i]].first, y = edges[qi[i]].second;
int z = g.lca(x, y) ^ x ^ y;
if (g.lca(z, qs[i]) == z) {
nd[qs[i]].insert(z);
}
}
dfs_st(rt, -1);
dfs_ans(rt, -1);
for (int i = 0; i < q; ++i) {
int x = edges[qi[i]].first, y = edges[qi[i]].second;
int z = g.lca(x, y) ^ x ^ y;
if (g.lca(z, qs[i]) == z) {
ll cans = ans[qs[i]][z];
if (cans == inf) cout << "oo\n";
else cout << cans << "\n";
} else {
cout << "escaped\n";
}
}
return 0;
}
