#include <bits/stdc++.h>
using namespace std;
vector<long long int>lcasum[100000],lcamin[100000],lca[100000],d(100000),v(100000);
vector<pair<int,int>>g[100000],edge;
bool vis[100000]={0};
long long Maxn=1e15;
void dfs1(int a,int b)
{
v[a]=Maxn;
if(vis[a])v[a]=0;
for(auto i:g[a])
{
if(i.first!=b)
{
d[i.first]=d[a]+1;
dfs1(i.first,a);
v[a]=min(v[a],v[i.first]+i.second);
}
}
}
void dfs(int a,int b,long long int sum)
{
lca[a].push_back(b);
lcasum[a].push_back(sum);
lcamin[a].push_back(v[a]);
for(int i=1;i<20;i++)
{
lca[a].push_back(lca[lca[a][i-1]][i-1]);
lcasum[a].push_back(lcasum[a][i-1]+lcasum[lca[a][i-1]][i-1]);
lcamin[a].push_back(min(lcamin[a][i-1],lcasum[a][i-1]+lcamin[lca[a][i-1]][i-1]));
}
for(auto i:g[a])
{
if(i.first!=b)
{
dfs(i.first,a,i.second);
}
}
}
long long int lcaq(int a,int b)
{
if(d[a]<d[b])return -1;
long long int sum=0,res=Maxn;
for(int i=19;i>=0;i--)
{
if(d[lca[a][i]]>=d[b])
{
res=min(res,sum+lcamin[a][i]);
sum+=lcasum[a][i];
a=lca[a][i];
}
}
if(a!=b)return -1;
return min(res,sum+lcamin[a][0]);
}
int main()
{
int n,m,q,k,a,b,c;
cin>>n>>m>>q>>k;
k--;
for(int i=0;i<n-1;i++)
{
cin>>a>>b>>c;
g[a-1].push_back({b-1,c});
g[b-1].push_back({a-1,c});
edge.push_back({a-1,b-1});
}
for(int i=0;i<m;i++)
{
cin>>a;
vis[a-1]=1;
}
dfs1(k,k);
dfs(k,k,0);
for(int i=0;i<q;i++)
{
cin>>a>>b;
if(d[edge[a-1].first]<d[edge[a-1].second])a=edge[a-1].second;
else a=edge[a-1].first;
long long int res=lcaq(b-1,a);
if(res==-1)cout<<"escaped";
else if(res==Maxn)cout<<"oo";
else cout<<res;
cout<<"\n";
}
return 0;
}
