import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
class Main {
static ArrayList<Pair<Integer,Integer> >v[] = new ArrayList[100009];
static int N,S,Q,E;
static int R[] = new int[100009];
static int flag[] = new int[100009];
static int dp[][] = new int[100009][32];
static long dis[] = new long[100009];
static long mn[] = new long[100009];
static long dpMn[][] = new long[100009][32];
static int w[] = new int[100009];
static Pair<Integer,Integer>edges[] = new Pair[100009];
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String[] s = reader.readLine().split(" ",0);
N = Integer.parseInt(s[0]);S = Integer.parseInt(s[1]);Q = Integer.parseInt(s[2]);E = Integer.parseInt(s[3]);
E--;
for(int i=0;i<N;i++){
v[i] = new ArrayList<>();
}
for(int i=0;i<N-1;i++){
s = reader.readLine().split(" ",0);
int a = Integer.parseInt(s[0]);
int b = Integer.parseInt(s[1]);
int c = Integer.parseInt(s[2]);
a--;b--;
v[a].add(new Pair<>(b,c));
v[b].add(new Pair<>(a,c));
edges[i] = new Pair<>(a,b);
}
for(int i=0;i<S;i++){
s = reader.readLine().split(" ",0);
R[i] = Integer.parseInt(s[0]);
R[i]--;
flag[R[i]] = 1;
}
dfs1(E,E);
dfs2(E,E);
for(int i=0;i<N;i++)mn[i] -= 2*dis[i];
for(int i=1;i<=30;i++){
for(int j=0;j<N;j++){
dpMn[j][i] = min(dpMn[j][i-1],dpMn[dp[j][i-1]][i-1]);
dp[j][i] = dp[dp[j][i-1]][i-1];
}
}
for(int i=0;i<Q;i++){
s = reader.readLine().split(" ",0);
int a = Integer.parseInt(s[0]);
int b = Integer.parseInt(s[1]);
a--;b--;
int p = edges[a].first;
if(w[edges[a].first]<w[edges[a].second]){
p = edges[a].second;
}
if(LCA(b,p) != p){
System.out.println("escaped");
continue;
}
long temp = dis[b];
long min = min(mn[b],mn[p]);
int l = w[b]-w[p];
for(int j=0;j<=30;j++){
if((l&(1<<j))>0){
min = min(min,dpMn[b][j]);
b = dp[b][j];
}
}
if(min+temp >= 1000000000000000l){
System.out.println("oo");
}
else
System.out.println(min+temp);
}
}
static long min(long a,long b){
if(a<b)return a;
return b;
}
static void dfs1(int node,int p){
w[node] = w[p] + 1;
dp[node][0] = p;
for(int i=0;i<v[node].size();i++){
int u = v[node].get(i).first;
if(u == p)continue;;
dis[u] = dis[node] + v[node].get(i).second;
dfs1(u,node);
}
}
static void dfs2(int node,int p){
if(flag[node]==1)
mn[node] = dis[node];
else
mn[node] = 1000000000000000000l;
for(int i=0;i<v[node].size();i++){
int u = v[node].get(i).first;
if(u == p)continue;
dfs2(u,node);
mn[node] = min(mn[node],mn[u]);
}
dpMn[node][0] = mn[node];
}
static int LCA(int a,int b){
if(w[a]<w[b]){
int t = a;
a = b;
b = t;
}
int l = w[a] - w[b];
for(int i=0;i<=30;i++){
if((l&(1<<i))>0){
a = dp[a][i];
}
}
for(int i=30;i>=0;i--){
if(dp[a][i] != dp[b][i]){
a = dp[a][i];
b = dp[b][i];
}
}
if(a == b)return a;
return dp[a][0];
}
}
class Pair<U,V>{
public U first;
public V second;
Pair(U a,V b){
first = a;
second = b;
}
}
