#include <iostream>
#include <vector>
#include <queue>
using namespace std;
#define int long long
#define pii pair<int,int>
int logn=18;
struct CELL{
int node,w,id;
};
int t=0;
bool is_ancestor(int a,int b,vector<pii>& time){
if(time[a].first<time[b].first&&time[a].second>time[b].second)return true;
return false;
}
int get_par(int a,int x,vector<vector<int>>& par){
for(int i=logn-1;i>=0;i--){
if(x&(1<<i))a=par[a][i];
}
return a;
}
bool escape(int anc,int x,vector<vector<int>>& p,vector<int>& depth,vector<pii>& time){
int dif=depth[x]-depth[anc];
if(get_par(x,dif,p)==anc)return false;
return true;
}
void dfs(int a,int par,vector<vector<CELL>>& g,vector<pii>& time,vector<vector<int>>& p,vector<int>& depth){
time[a].first=t;
t++;
p[a][0]=par;
depth[a]=depth[par]+1;
for(int j=1;j<logn;j++){
p[a][j]=p[p[a][j-1]][j-1];
}
for(auto v:g[a]){
if(par==v.node)continue;
dfs(v.node,a,g,time,p,depth);
}
time[a].second=t;
t++;
}
int dijkstra(int a,int i,vector<vector<CELL>>& g,vector<int>& shop){
priority_queue<pii> pq;
pq.push({0,a});
int n=g.size();
vector<int> dist(n,1e18);
dist[a]=0;
while(!pq.empty()){
int u=pq.top().second,d=-pq.top().first;
pq.pop();
if(dist[u]<d)continue;
for(auto v:g[u]){
if(v.id==i)continue;
if(dist[v.node]>dist[u]+v.w){
dist[v.node]=dist[u]+v.w;
pq.push({-dist[v.node],v.node});
}
}
}
int ans=1e18;
for(int s:shop){
ans=min(ans,dist[s]);
}
return ans;
}
signed main(){
int n,s,q,e,x,y,w;
cin>>n>>s>>q>>e;
e--;
vector<pii> edges(n-1),time(n);
vector<vector<CELL>> g(n,vector<CELL>());
vector<vector<int>> p(n,vector<int>(logn));
vector<int> shop(s),depth(n);
for(int i=0;i<n-1;i++){
cin>>x>>y>>w;
x--;y--;
g[x].push_back({y,w,i});
g[y].push_back({x,w,i});
edges[i]={x,y};
}
for(int i=0;i<s;i++){
cin>>shop[i];
shop[i]--;
}
dfs(e,e,g,time,p,depth);
//for(int i=0;i<n;i++)cout<<depth[i]<<' ';
while(q--){
cin>>x>>y;
x--;y--;
int anc=edges[x].first;
if(time[edges[x].second]>time[anc])anc=edges[x].second;
//cout<<anc<<'\n';
if(escape(anc,y,p,depth,time))cout<<"escaped\n";
else{
if(n*q>1e6){
cout<<"0\n";
}else{
int ans=dijkstra(y,x,g,shop);
if(ans==1e18)cout<<"oo\n";
else cout<<ans<<'\n';
}
}
}
}
