#include<bits/stdc++.h>
using namespace std;

#define int long long
typedef vector<int>vint;
typedef pair<int,int>pint;
typedef vector<pint>vpint;
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
#define all(v) (v).begin(),(v).end()
#define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++)
#define pb push_back
#define fi first
#define se second
template<typename A,typename B>inline void chmin(A &a,B b){if(a>b)a=b;}
template<typename A,typename B>inline void chmax(A &a,B b){if(a<b)a=b;}


struct LinkCutTree{;
    struct Node{
        Node *lp,*rp,*pp;
        bool rev;
        int val,agg;
        Node():lp(0),rp(0),pp(0),rev(0){}
        bool isRoot(){
            return !pp||(pp->lp!=this&&pp->rp!=this);
        }

        void push(){
            if(!rev)return;
            if(lp)lp->rev^=1;
            if(rp)rp->rev^=1;
            swap(lp,rp);
            rev=false;
        }

        void push_all(){
            if(!isRoot())pp->push_all();
            push();
            if(lp)lp->push();
            if(rp)rp->push();
        }

        void update(){
            agg=val;
            if(lp)chmin(agg,lp->agg);
            if(rp)chmin(agg,rp->agg);
        }

        void rotR(){
            Node *q=pp,*r=q->pp;
            if((q->lp=rp))rp->pp=q;
            rp=q;q->pp=this;
            if((pp=r)){
                if(r->lp==q)r->lp=this;
                if(r->rp==q)r->rp=this;
            }
            q->update();
            update();
        }

        void rotL(){
            Node *q=pp,*r=q->pp;
            if((q->rp=lp))lp->pp=q;
            lp=q;q->pp=this;
            if((pp=r)){
                if(r->lp==q)r->lp=this;
                if(r->rp==q)r->rp=this;
            }
            q->update();
            update();
        }


        void splay(){
            push_all();
            while(!isRoot()){
                Node *q=pp;
                if(q->isRoot()){
                    if(q->lp==this)rotR();
                    else rotL();
                }
                else{
                    Node *r=q->pp;
                    if(r->lp==q){
                        if(q->lp==this){q->rotR();rotR();}
                        else {rotL();rotR();}
                    }
                    else{
                        if(q->rp==this){q->rotL();rotL();}
                        else{rotR();rotL();}
                    }
                }
            }
        }

        void expose(){
            Node *rp=NULL;
            for(Node *p=this;p;p=p->pp){
                p->splay();
                p->rp=rp;
                rp=p;
                p->update();
            }
            splay();
        }
    };

    Node *nodes;
    LinkCutTree(int n){nodes=new Node[n];}

    //???(v->v??????)?????????
    void cut(int v){
        nodes[v].expose();
        Node *p=nodes[v].lp;
        nodes[v].lp=NULL;
        p->pp=NULL;
        nodes[v].update();
    }

    //???(v->u)?????????
    void link(int v,int u){
        nodes[v].expose();
        nodes[u].expose();
        nodes[v].pp=&nodes[u];
        nodes[u].rp=&nodes[v];
        nodes[u].update();
    }

    int lca(int a,int b){
        nodes[a].expose();
        nodes[b].expose();

        bool sameTree=false;
        Node *ret=&nodes[a];
        for(Node *x=&nodes[a];x;x=x->pp){
            if(x->pp&&x->isRoot())ret=x->pp;
            if(x==&nodes[b])sameTree=true;
        }
        return sameTree?(ret-nodes):-1;
    }

    void evert(int v){
        nodes[v].expose();
        nodes[v].rev^=1;
    }

    int findRoot(int v){
        Node *p=&nodes[v];
        p->expose();
        while(p->lp)p=p->lp;
        p->splay();
        return p-nodes;
    }

    int query(int u,int v){
        evert(u);
        nodes[v].expose();
        return nodes[v].agg;
    }
};

const int INF=1001001001ll;

int N,M,K,Q;
int A[222222],B[222222],C[222222];
vpint G[222222];
int dist[222222];
signed main(){
    scanf("%lld%lld%lld%lld",&N,&M,&K,&Q);
    rep(i,M){
        scanf("%lld%lld%lld",&A[i],&B[i],&C[i]);
        A[i]--;B[i]--;
        G[A[i]].pb({B[i],C[i]});
        G[B[i]].pb({A[i],C[i]});
    }

    fill_n(dist,N,INF);
    priority_queue<pint,vector<pint>,greater<pint>>que;
    rep(i,K){
        int v;scanf("%lld",&v);v--;
        dist[v]=0;
        que.push({0,v});
    }
    while(que.size()){
        int c,v;
        tie(c,v)=que.top();
        que.pop();
        if(dist[v]<c)continue;
        for(auto &e:G[v]){
            if(dist[e.fi]<=c+e.se)continue;
            dist[e.fi]=c+e.se;
            que.push({dist[e.fi],e.fi});
        }
    }


    //cout<<"-----------------"<<endl;
    //rep(i,N)cout<<dist[i]<<" ";cout<<endl;

    LinkCutTree lct(N);
    rep(i,N)lct.nodes[i].val=lct.nodes[i].agg=dist[i];
    vector<pint>es;
    rep(i,M)es.pb({min(dist[A[i]],dist[B[i]]),i});
    sort(all(es));reverse(all(es));
    rep(i,es.size()){
        int j=es[i].se;
        if(lct.findRoot(A[j])==lct.findRoot(B[j]))continue;
        lct.evert(A[j]);
        lct.link(A[j],B[j]);
    }

    /*
    cout<<endl;
    rep(i,N)cout<<lct.nodes[i].isRoot()<<" ";cout<<endl;
    rep(i,N){
        cout<<i+1<<" ";
        if(lct.nodes[i].pp)cout<<lct.nodes[i].pp-lct.nodes+1<<endl;
        else cout<<-1<<endl;
    }

    cout<<"---------"<<endl;
*/


    while(Q--){
        int a,b;
        scanf("%lld%lld",&a,&b);
        a--;b--;
        printf("%lld\n",lct.query(a,b));
    }
    return 0;
}

Measured memory_bytes: 33352