//In His Name
#include <bits/stdc++.h>
//#pragma GCC optimization("O3")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("avx2")
using namespace std;
#define ll long long
#define int ll
typedef pair<int, int> pii;
#define F first
#define S second
#define pb push_back
#define bug(x) cout << "Ah shit , here we go again : " << x << endl
#define all(x) x.begin() , x.end()
const int maxn = 1e5 + 10, MOD = 1e9 + 7 , Lg = 20;
const ll INF = 1e18 + 100;
int n , s , q , root , par[maxn][Lg] , mini[maxn][Lg] , st[maxn] , fn[maxn] , t , val[maxn];
vector<pii> adj[maxn] , edge;
bool shop[maxn];
void Dfs(int v = root , int p = 0){
par[v][1] = p , st[v] = ++t , par[v][0] = v;
for(int i = 2 ; i < Lg ; i++) par[v][i] = par[par[v][i-1]][i-1] , mini[v][i] = INF;
mini[v][0] = mini[v][1] = INF;
for(pii u : adj[v]){
if(u.S == p) continue;
val[u.S] = val[v] + u.F;
Dfs(u.S , v);
mini[v][0] = min(mini[v][0] , mini[u.S][0] + u.F);
}
if(shop[v]) mini[v][0] = 0;
fn[v] = t;
}
void BL(int p , int v){
int res = mini[v][0] , x = v;
for(int i = 19 ; i >= 1 ; i--){
if(st[par[v][i]] >= st[p] and fn[p] >= fn[par[v][i]]) {
res = min(res, mini[v][i]);
v = par[v][i];
}
}
if(res >= 1e14) cout << "oo\n";
else cout << res + val[x] << '\n';
}
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(0) , cout.tie(0);
cin >> n >> s >> q >> root;
edge.pb({0 , 0});
for(int i = 1 ; i < n ; i++){
int u , v , w;
cin >> u >> v >> w;
adj[v].pb({w , u});
adj[u].pb({w , v});
edge.pb({u , v});
}
for(int i = 1 ; i <= s ; i++){
int x;
cin >> x;
shop[x] = true;
}
Dfs();
for(int i = 1 ; i <= n ; i++) mini[i][0] -= val[i];
for(int i = 1 ; i <= n ; i++) for(pii u : adj[i]) if(u.S != par[i][1]) mini[u.S][1] = min(mini[u.S][0] , mini[i][0]);
for(int i = 2 ; i < Lg ; i++)
for(int v = 1 ; v <= n ; v++)
mini[v][i] = min(mini[v][i-1] , mini[par[v][i]][i-1]);
while(q--){
int x , y;
cin >> x >> y;
int u = edge[x].F , v = edge[x].S;
if(st[u] > st[v]) swap(u , v);
if(st[v] <= st[y] and fn[v] >= fn[y]) BL(v , y);
else cout << "escaped\n";
}
}
