#include <bits/stdc++.h>
#define ll long long
//#define int ll
using namespace std;

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

int n,k,p,m;
int infractiune[155][3505];
int cost[155][155];
vector < pair < int ,int > > G[155];
int dp[155][3505];

main()
{
    f>>n>>m>>k>>p;

    for(int i=1;i<=m;++i)
    {
        int a,b,c;
        f>>a>>b>>c;
        cost[a][b]=cost[b][a]=c;
        G[a].push_back({b,c});
        G[b].push_back({a,c});

        //g<<a<< ' '<<b<< ' '<<c<< '\n';
    }

    for(int i=1;i<=k;++i)
    {
        int a,b,c;
        f>>a>>b>>c;
        infractiune[a][b]+=c;
    }

    for(int i=1;i<=n;++i)
        for(int j=0;j<=3500;++j) dp[i][j]=-1;
    dp[1][0]=infractiune[1][0];
    for(int timp = 1 ; timp<=3500; ++timp )
    {
        for(int nod = 1 ; nod<=n;++nod)
        {
            dp[nod][timp]=max(dp[nod][timp],dp[nod][timp-1]);
            for(auto x:G[nod])
            {
                int timpdrum = x.second;
                int vecin = x.first;
                if(timp>=timpdrum)
                    dp[nod][timp] = max(dp[nod][timp],dp[vecin][timp-timpdrum]);
            }
            if(dp[nod][timp]!=-1) dp[nod][timp]+=infractiune[nod][timp];
        }
    }

    for(int i=1;i<=p;++i)
    {
        int a,b;
        f>>a>>b;
        g<<dp[a][b]<<'\n';
        //g<<a<< ' '<<b<<'\n';
    }

    return 0;
}