#include <bits/stdc++.h>
#define pb push_back
using namespace std;
#define F first
#define S second
#define int long long
#define FOR(x, n, m, d) for(int x = n; x <= m; x += d)
#define FORR(x, n, m, d) for(int x = n; x >= m; x -= d)
#define nikita ios_base::sync_with_stdio(0), cin.tie(0);
const int N = 1e5+150;
int n,m,k,tt,ans,l, r, x, y, cnt, ko = 0;
int b[N],a[N], sum, root[N], block = 620, d[N], c[N];
string s[N], str;
vector<pair<int, int>>g[N];
bool f = 0;
map<pair<int, int>, int>mp;
void dfs(int v, int p = 0, int sum = 0){
if(cnt == v){f = 1;return;}
if(c[v]){
ko = min(ko, sum);
}
for(auto i : g[v]){
if(i.F != p && mp[{v, i.F}] == 0){
dfs(i.F, v, sum + i.S);
}
}
}
void solve(){
nikita
cin >> n >> m >> k >> cnt;
FOR(i, 1, n-1, 1){
cin >> a[i] >> b[i] >> r;
x = a[i], y = b[i];
g[x].pb({y, r}), g[y].pb({x, r});
}
FOR(i, 1, m, 1)cin >> d[i], c[d[i]] = 1;
FOR(i, 1, k, 1){
f = 0;
ko = 1e18;
cin >> x >> y;
mp[{a[x], b[x]}] = 1, mp[{b[x], a[x]}] = 1;
dfs(y);
mp[{a[x], b[x]}] = mp[{b[x], a[x]}] = 0;
if(f)cout << "escaped\n";
else if(ko != 1e18)cout << ko << '\n';
else cout << "oo\n";
}
}
signed main()
{
nikita
tt = 1;
if(!tt)cin >> tt;
FOR(i, 1, tt, 1){
solve();
}
}
