#include <fstream>
#include <vector>
#include <cstring>
using namespace std;
int main()
{
    ifstream in("amenzi.in");
    ofstream out("amenzi.out");
    int n, m, k, p, i, j, q, c, u, v, time, node;
    in>>n>>m>>k>>p;

    vector< vector< pair<int, int> > > g(n+1);
    for(i=1; i<=m; i++)
    {
        in>>u>>v>>time;
        g[u].push_back(make_pair(v, time));
        g[v].push_back(make_pair(u, time));
    }

    vector< vector<int> > cost(3505, vector<int>(n+1));
    for(i=1; i<=k; i++)
    {
        in>>u>>v>>c;
        cost[v][u]=c;
    }

    vector< vector<int> > dp(3505, vector<int>(n+1, -1));
    dp[0][1]=0;

    for(i=1; i<=3500; i++)
        for(j=1; j<=n; j++)
        {

            for(q=0; q<g[j].size(); q++)
            {
                node=g[j][q].first;
                time=g[j][q].second;
                if(i-time>=0)
                    dp[i][j]=max(dp[i-time][node], dp[i][j]);

            }
            dp[i][j]=max(dp[i][j], dp[i-1][j]);
            if(dp[i][j]>=0)
                dp[i][j]+=cost[i][j];
        }

    for(i=1; i<=p; i++)
    {
        in>>u>>time;
        if(dp[time][u]<0)
            out<<-1<<'\n';
        else
            out<<dp[time][u]<<'\n';
    }

    return 0;
}