#include <bits/stdc++.h>
using namespace std;
#define int long long
#define double long double
#define FOR(i, l, r, d) for(int i=(l); i<=(r); i+=(d))
#define szof(x) ((int)(x).size())
#define vi vector<int>
#define pii pair<int, int>
#define F first
#define S second
#define pb push_back
#define eb emplace_back
#define mkp make_pair
const int INF = INT_MAX;
const int LNF = INF*INF;
const int MOD = 1000000007;
const int mod = 998244353;
const double eps = 1e-12;
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
const int MAX = 100010;
// in
int n, q;
int root;
int shops;
int eu[MAX], ev[MAX], ew[MAX]; // i-th edge = (eu[i], ev[i])
vector<pii> edge[MAX]; // to, dis
bool isshop[MAX];
// HLD
int sz[MAX], par[MAX], dep[MAX], fr[MAX], heavy[MAX], id[MAX], from[MAX], to[MAX];
int ts = 1, ets;
// sweep line
int dp[MAX];
vector<vi> EV;
// modify : time, insert/erase, val
// query : time, 2
// sparse table
int st[MAX][20];
// res = min(dep[shop] - 2*dep[lca]) + dep[qv]
void find_sz(int v, int pv){
// find sz, par, dep, heavy
par[v] = pv;
sz[v] = 1;
from[v] = ets++;
int Max = 0;
heavy[v] = -1;
for(pii e : edge[v]){
int i = e.F, dd = e.S;
if(i == pv) continue;
dep[i] = dep[v] + dd;
find_sz(i, v);
sz[v] += sz[i];
if(sz[i] > Max){
Max = sz[i];
heavy[v] = i;
}
}
to[v] = ets++;
}
void HLD(int v, int pv, int frv){
// HLD subtree v
fr[v] = frv;
id[v] = ts++;
if(heavy[v] != -1) HLD(heavy[v], v, frv);
for(pii e : edge[v]){
int i = e.F;
if(i == pv or i == heavy[v]) continue;
HLD(i, v, i);
}
}
void add_seg(int v){
int val = dep[v];
while(v != root){
// node id : [fr[v], v]
// st id : [id[fr[v]], id[v]]
EV.pb({id[fr[v]], 1, val});
EV.pb({id[v] + 1, -1, val});
v = par[fr[v]];
}
// v == root
EV.pb({id[v], 1, val});
EV.pb({id[v] + 1, -1, val});
}
inline int query_min(int L, int R){
int rk = __lg(R - L + 1);
//int ret = min(st[L][rk], st[R - (1<<rk) + 1][rk]);
//cerr<<"query_min("<<L<<", "<<R<<") = "<<ret<<endl;
return min(st[L][rk], st[R - (1<<rk) + 1][rk]);
}
inline int isanc(int u, int v){
return (from[u] <= from[v] and to[v] <= to[u]);
}
int query_res(int u, int v){
int ret = LNF;
while(fr[u] != fr[v]){
ret = min(ret, query_min(id[fr[v]], id[v]));
v = par[fr[v]];
}
ret = min(ret, query_min(id[u], id[v]));
return ret;
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
// in
cin>>n>>shops>>q>>root;
FOR(i, 1, n-1, 1){
cin>>eu[i]>>ev[i]>>ew[i];
edge[eu[i]].eb(ev[i], ew[i]);
edge[ev[i]].eb(eu[i], ew[i]);
}
FOR(i, 1, shops, 1){
int C;
cin>>C;
isshop[C] = 1;
}
// HLD
find_sz(root, root);
HLD(root, root, root);
/*
cerr<<"HLD : ";
FOR(i, 1, n, 1){
cerr<<id[i]<<" ";
}
cerr<<endl;
*/
// HLD ok
// sweep line :
// events
FOR(i, 1, n, 1){
if(isshop[i]) add_seg(i);
EV.pb({i, 2});
}
sort(EV.begin(), EV.end());
// min(dep[shop])
multiset<int> owo;
for(vi E : EV){
int type = E[1];
if(type < 2){ // modify
int val = E[2];
if(type == 1){ // insert
owo.insert(val);
}
else if(type == -1){ // erase
owo.erase(owo.find(val));
}
}
else if(type == 2){ // query
int Time = E[0];
if(!owo.empty()) dp[Time] = *owo.begin();
else dp[Time] = LNF;
}
}
// min(dep[shop]) - 2*dep[lca]
FOR(i, 1, n, 1){
dp[id[i]] -= 2 * dep[i];
}
/*
cerr<<"dp : ";
FOR(i, 1, n, 1){
if(dp[i] < LNF / 2) cerr<<dp[i]<<" ";
else cerr<<"- ";
}
cerr<<endl;
*/
// dp ok
// sparse table
FOR(i, 1, n, 1){
st[i][0] = dp[i];
}
FOR(j, 1, 19, 1){
FOR(i, 1, n, 1){
int ii = i + (1<<(j-1));
if(ii <= n) st[i][j] = min(st[i][j-1], st[ii][j-1]);
else st[i][j] = st[i][j-1];
}
}
// query
while(q--){
int ie, qv;
cin>>ie>>qv;
int iu = eu[ie], iv = ev[ie];
if(isanc(iu, qv) and isanc(iv, qv)){
// go to shop
if(dep[iu] < dep[iv]) swap(iu, iv);
// can only move in subtree iu
// query : node iu ~ node qv
// res = min(dep[shop] - 2*dep[lca]) + dep[qv]
int res = query_res(iu, qv) + dep[qv];
if(res > LNF / 2) cout<<"oo"<<'\n';
else cout<<res<<'\n';
}
else{
// escaped
cout<<"escaped"<<'\n';
}
}
return 0;
}
