#include <bits/stdc++.h>

using namespace std;

const int N=155;
const int M=3505;
const int inf=(1<<30)-1;

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

int n,m,k,p;
int d,b,c;
int dist[N][N];

struct Infractiune{
    int city,time,value;
}a[4*M],x;

int dp[M][N];

void RoyFloyd()
{
    for(int k=1;k<=n;++k){
        for(int i=1;i<=n;++i){
            for(int j=1;j<=n;++j){
                dist[i][j]=min(dist[i][j],dist[i][k]+dist[k][j]);
            }
        }
    }
}

bool comp(Infractiune A,Infractiune B) {
    if(A.time == B.time) return (A.city < B.city);
    return (A.time < B.time);
}

int main()
{
    for(int i=1;i<=N-5;++i) for(int j=1;j<=N-5;++j) if(i!=j) dist[i][j]=inf;

    for(int i=0;i<=M-5;++i) for(int j=1;j<=N-5;++j) dp[i][j]=-inf;

    f>>n>>m>>k>>p;
    for(int i=1;i<=m;++i) {
        f>>d>>b>>c;
        dist[d][b]=dist[b][d]=c;
    }

    RoyFloyd();

//    for(int i=1;i<=5;++i, cout<<endl) for(int j=1;j<=5;++j) cout<<dist[i][j]<<' ';
//    cout<<endl<<endl;

    for(int i=1;i<=k;++i) f>>a[i].city>>a[i].time>>a[i].value;
    sort(a+1,a+k+1,comp);

    dp[0][1]=0;
    d=0;
    a[0].city = 1; a[0].time=0; a[0].value = 0;

    for(int i=0;i<=M-5;++i) {
        for(int j=1;j<=n;++j) {
            if(i)
                dp[i][j]=max(dp[i][j],dp[i-1][j]);
            if(a[d].city == j && a[d].time == i) {
                dp[i][j]+=a[d].value;
                for(int k=1;k<=n;++k) {
                   if(i+dist[j][k] < M) dp[i+dist[j][k]][k] = max(dp[i+dist[j][k]][k],dp[i][j]);
                }
                ++d;
            }
        }
    }

    for(int i=0;i<=M-5;++i) for(int j=1;j<=n;++j) if(dp[i][j]<0) dp[i][j]=-1;

    while(p--) {
        f>>b>>c;
        g<<dp[c][b]<<'\n';
    }

    return 0;
}