#include <bits/stdc++.h>
#define pb push_back
#define F first
#define S second
#define all(v) v.begin(),v.end()
using namespace std;
typedef long long ll;
const int maxn = 1e5 + 5;
int n,s,q,e,a[maxn],x[maxn],y[maxn],z[maxn],c[maxn],z1[maxn],z2[maxn];
vector <pair<int,int>> g[maxn];
ll d[maxn];
int xx;
void dfs(int v, int u){
for(auto i : g[v]){
if(i.F == u) continue;
if(min(i.F,v) == x[z1[xx]] && max(i.F,v) == y[z1[xx]]){
continue;
}
d[i.F] = d[v] + i.S;
dfs(i.F,v);
}
}
int up[maxn][21],tin[maxn],tout[maxn],timer;
int dep[maxn];
void dfs2(int v, int u){
tin[v] = ++timer;
dep[v] = dep[u] + 1;
up[v][0] = u;
for(int i = 1; i <= 20; i++) up[i][v] = up[up[i - 1][v]][i - 1];
for(auto i : g[v]){
if(i.F == u) continue;
dfs2(i.F,v);
}
tout[v] = timer;
}
bool check(int v, int u){
return tin[v] <= tin[u] && tout[u] <= tin[v];
}
int lca(int v, int u){
if(check(v,u)) return v;
if(check(u,v)) return u;
for(int i = 20; i >= 0; i--){
if(!check(up[v][i], u)) {
v = up[v][i];
}
}
return up[v][0];
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> s >> q >> e;
for(int i = 1; i < n; i++){
cin >> x[i] >> y[i] >> z[i];
if(x[i] > y[i]) swap(x[i],y[i]);
g[x[i]].pb({y[i],z[i]});
g[y[i]].pb({x[i],z[i]});
}
for(int i = 1; i <= s; i++){
cin >> c[i];
}
for(int i = 1; i <= q; i++){
cin >> z1[i] >> z2[i];
}
if(s == n){
dfs2(1,1);
for(int i = 1; i <= q; i++){
int papa = lca(z2[i],e);
int v1,v2;
v1 = x[z1[i]];
v2 = y[z1[i]];
if(dep[v1] > dep[v2]) swap(v1,v2);
if(check(papa,v1) && (check(v2,e) || check(v2,z2[i]))){
cout << "escaped\n";
}
else {
cout << "0\n";
}
}
}
else{
for(int i = 1; i <= q; i++){
for(int j = 1; j <= n; j++) d[j] = -1;
xx = i;
d[z2[i]] = 0;
dfs(z2[i],z2[i]);
if(d[e] != -1){
cout << "escaped\n";
}
else {
ll mn = 1e18;
for(int j = 1; j <= s; j++){
if(d[c[j]] != -1) mn = min(mn, d[c[j]]);
}
if(mn == 1e18) cout << "oo\n";
else cout << mn << '\n';
}
}
}
return 0;
}
