///breaker
///every second counts
#include<bits/stdc++.h>
using namespace std;
struct duongdi{
int u,w;
bool operator<(const duongdi&d2)const{
return w > d2.w;
}
};
struct edge
{
int u,v,w;
bool operator<(const edge&b)const{
return w>b.w;
}
};
const int maxn=1e5+7;
edge e[5*maxn];
vector<pair<int, int>>adj1[maxn],adj2[maxn];
int d[maxn],r[maxn],p[25][maxn], dp[25][maxn];
int h[maxn];
priority_queue<duongdi>q;
int sz[maxn];
int Find(int u){
return ((u==r[u])?u:r[u]=Find(r[u]));
}
void dfs(int u, int pa){
for(auto[v,w]:adj2[u]){
if(v == pa) continue;
p[v][0] = u;
dp[v][0] = w;
h[v]=h[u]+1;
dfs(v, u);
}
}
int lca(int u, int v){
if(h[u]<h[v])swap(u, v);
int diff=h[u]-h[v];
int mn=1e9+7;
for(int i=20;i>=0;i--)if((diff>>i)&1){
mn=min(mn,dp[u][i]);
u=p[u][i];
}
if(u == v) return mn;
for(int i = 20; i>=0; --i){
if(p[u][i]!=p[v][i]){
mn=min({mn, dp[u][i], dp[v][i]});
u=p[u][i];
v=p[v][i];
}
}
return min({mn,dp[u][0],dp[v][0]});
}
int n,m,k,t;
int main(){
// freopen("walk.inp","r",stdin);
// freopen("walk.out","w",stdout);
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin>>n>>m>>k>>t;
for(int i=0;i<=20;i++){
for(int j=1;j<=n;j++){
dp[j][i]=1e9+7;
}
}
for(int i = 0; i<m; ++i){
int u,v,w;
cin>>u>>v>>w;
adj1[u].push_back({v, w});
adj1[v].push_back({u, w});
e[i].u=u;
e[i].v=v;
}
for(int i = 1; i<=n; ++i)d[i] = 1e9;
for(int i = 1; i<=n; ++i){
r[i] = i;
sz[i]=1;
}
for(int i = 1; i<=k; ++i){
int u;
cin>>u;
d[u]=0;
q.push({u, d[u]});
}
while(!q.empty()){
int u=q.top().u;
int du=q.top().w;
q.pop();
if(d[u]<du)continue;
for(auto [v,w]:adj1[u]){
if(d[v]>du+w){
d[v]=du+w;
q.push({v, d[v]});
}
}
}
for(int i=0;i<m;i++){
e[i].w=min(d[e[i].u],d[e[i].v]);
}
sort(e,e+m);
for(int i=0;i<m;i++){
int u=e[i].u,v=e[i].v,w=e[i].w;
if(Find(u)!=Find(v)){
u=Find(u);
v=Find(v);
adj2[u].push_back({v, w});
adj2[v].push_back({u, w});
if(sz[u]<sz[v])swap(u,v);
sz[u]+=sz[v];
r[v]=u;
}
}
dfs(1,0);
for(int j = 1; j<=20; ++j){
for(int i = 1; i<=n; ++i){
p[i][j]=p[p[i][j-1]][j-1];
dp[i][j] = min(dp[i][j-1], dp[p[i][j-1]][j-1]);
}
}
while(t--){
int u,v;
cin>>u>>v;
cout<<lca(u, v)<<"\n";
}
return 0;
}
