#include <cstdio>
#include <stdio.h>
#include <stdbool.h>
#include <iostream>
#include <map>
#include <vector>
#include <climits>
#include <stack>
#include <string>
#include <queue>
#include <algorithm>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cmath>
#include <cctype>
#include <bitset>
#include <iomanip>
#include <cstring>
#include <numeric>
#include <cassert>
using namespace std;
#define int long long
#define pii pair<int, int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
struct ooga{
int s, e, m, val;
ooga *l, *r;
ooga(int S, int E){
s = S, e = E, m = (s+e)/2;
val=LLONG_MAX/2;
if (s!=e){
l = new ooga(s, m);
r = new ooga(m+1, e);
}
}
void up(int ind, int nv){
if (s==e)val=nv;
else{
if (ind<=m)l->up(ind, nv);
else r->up(ind, nv);
val = min(l->val, r->val);
}
}
int query(int left, int right){
if (s==left && e==right)return val;
if (right<=m)return l->query(left, right);
else if (left>m)return r->query(left, right);
else return min(l->query(left, m), r->query(m+1, right));
}
}*st[100005];
int counter=0, depth[100005], dist[100005], in[100005], out[100005], par[100005], sz[100005], twok[100005][18];
vector<int> temp, inside[100005], lvl;
vector<pii> graph[100005];
void dfs(int node, int p, int dep, int d){
in[node]=++counter;
depth[node]=dep;
dist[node]=d;
twok[node][0]=p;
for (int i=1; i<18; ++i)twok[node][i]=twok[twok[node][i-1]][i-1];
for (auto num:graph[node])if (num.fi!=p)dfs(num.fi, node, dep+1, d+num.se);
out[node]=counter;
}
int kth(int a, int k){
for (int i=0; i<18; ++i)if (k&(1<<i))a=twok[a][i];
return a;
}
int lca(int a, int b){
if (depth[a]<depth[b])swap(a, b);
a=kth(a, depth[a]-depth[b]);
if (a==b)return a;
for (int i=17; i>=0; --i)if (twok[a][i]!=twok[b][i])a=twok[a][i], b=twok[b][i];
return twok[a][0];
}
int calc(int a, int b){
return dist[a]+dist[b]-2*dist[lca(a, b)];
}
int dfs_size(int node, int p){
temp.pb(in[node]);
sz[node]=1;
for (auto num:graph[node])if (num.fi!=p&&lvl[num.fi]==-1)sz[node]+=dfs_size(num.fi, node);
return sz[node];
}
int centroidfind(int node, int p, int size){
for (auto num:graph[node])if (num.fi!=p&&lvl[num.fi]==-1&&sz[num.fi]>size/2)return centroidfind(num.fi, node, size);
return node;
}
void build(int node, int p, int d){
temp.clear();
int c=centroidfind(node, p, dfs_size(node, p));
lvl[c]=d;
par[c]=p;
sort(temp.begin(), temp.end());
inside[c]=temp;
st[c] = new ooga(0, temp.size()-1);
for (auto num:graph[c])if (lvl[num.fi]==-1)build(num.fi, c, d+1);
}
void cupdate(int node){
for (int c=node; c!=-1; c=par[c])st[c]->up((lower_bound(inside[c].begin(), inside[c].end(), in[node])-inside[c].begin()), calc(node, c));
}
int cquery(int node, int a){
int res=LLONG_MAX/2;
for (int c=node; c!=-1; c=par[c]){
int low=(lower_bound(inside[c].begin(), inside[c].end(), in[a])-inside[c].begin());
int high=(upper_bound(inside[c].begin(), inside[c].end(), out[a])-inside[c].begin())-1;
if (low<=high)res=min(res, calc(c, node)+st[c]->query(low, high));
}
return res;
}
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, s, q, e, a, b, c;
cin>>n>>s>>q>>e;
pii edges[n+5];
lvl.resize(n+1, -1);
for (int i=1; i<n; ++i){
cin>>a>>b>>c;
graph[a].pb(mp(b, c));
graph[b].pb(mp(a, c));
edges[i]=mp(a, b);
}
dfs(e, e, 0, 0);
build(e, -1, 0);
while (s--)cin>>a, cupdate(a);
while (q--){
cin>>a>>b;
if (in[edges[a].fi]>in[edges[a].se])c=edges[a].fi;
else c=edges[a].se;
if (in[c]<=in[b]&&in[b]<=out[c]){
int res=cquery(b, c);
if (res==LLONG_MAX/2)cout<<"oo\n";
else cout<<res<<"\n";
}
else cout<<"escaped\n";
}
}
