#include <iostream>
#include <fstream>
#include <algorithm>

using namespace std;

ifstream f("amenzi.in");
ofstream g("amenzi.out");

struct amenzi{
    int n,t,val;
}v[12005];
int n,m,p,k,a[155][155],x,y,c,u;
int arb[155][3505],mx,d,node,r,fl;

///roy floyd pt distante minime intre noduri
///sortez infractiunile dupa timp
///pt infractiunea curenta caut una recenta de la care pot ajunge cu bani maximi
///querurile iar sortate si mers tot la fel

void talktomebaby()
{
    for(int K=1;K<=n;++K) for(int i=1;i<=n;++i) for(int j=1;j<=n;++j)
    if(i!=K && j!=K && a[i][K] && a[K][j] && (a[i][K]+a[K][j]<a[i][j] || a[i][j]==0)) a[i][j]=a[j][i]=a[i][K]+a[K][j];
}

bool comp(amenzi a,amenzi b){return(a.t<b.t);}

void update(int i,int nod,int lt,int rt,int poz)
{
    if(lt==rt)
    {
        arb[i][nod]=u;
        return;
    }
    int md=(lt+rt)/2;
    if(poz<=md) update(i,nod*2,lt,md,poz);
    else update(i,nod*2+1,md+1,rt,poz);

    arb[i][nod]=max(arb[i][nod*2],arb[i][nod*2+1]);
}

void query(int i,int nod,int lt,int rt,int x,int y)
{
    if(x>rt || y<lt) return;
    if(x<=lt && rt<=y)
    {
        r=max(r,arb[i][nod]);
        return;
    }
    int md=(lt+rt)/2;
    if(md>=x) query(i,nod*2,lt,md,x,y);
    if(md<y) query(i,nod*2+1,md+1,rt,x,y);
}

void thismadnesssogoodforme()
{
    for(int i=1;i<=k;++i)
    {
        node=v[i].n; mx=0;
        for(int j=1;j<=n;++j) if(node==j || a[node][j])
        {
            d=v[i].t-a[node][j]; r=0;
            query(j,1,0,3500,0,d);
            mx=max(mx,r);
        }
        u=v[i].val+mx;
        if(mx==0)
        {
            d=-1;
            if(a[node][1] || node==1) d=v[i].t-a[node][1];
        }
        if(d>=0) update(node,1,0,3500,v[i].t);
    }
}

void thatsthatshitivebeenon()
{
    for(int i=1;i<=p;++i)
    {
        f>>node>>fl; mx=0;
        for(int j=1;j<=n;++j) if(node==j || a[node][j])
        {
            d=fl-a[node][j]; r=0;
            query(j,1,0,3500,0,d);
            mx=max(mx,r);
        }
        g<<mx<<'\n';
    }
}

int main()
{
    f>>n>>m>>k>>p;
    for(int i=1;i<=m;++i) {f>>x>>y>>c; a[x][y]=a[y][x]=c;}
    talktomebaby();
    for(int i=1;i<=k;++i) {f>>v[i].n>>v[i].t>>v[i].val;}
    sort(v+1,v+k+1,comp);
    thismadnesssogoodforme();

    thatsthatshitivebeenon();
    return 0;
}