#include <bits/stdc++.h>
#define PII pair <int, int>
#define DIM 155
#define TMAX 3505

using namespace std;

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

int n, m, k, p;
int dp[TMAX][DIM], amenda[TMAX][DIM];
vector <PII> edges[DIM];

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

    for(int i = 1; i <= m; i++)
    {
        int x, y, cost;
        f >> x >> y >> cost;
        edges[x].push_back(make_pair(y, cost));
        edges[y].push_back(make_pair(x, cost));
    }

    for(int i = 1; i <= k; i++)
    {
        int x, cost, t;
        f >> x >> t >> cost;
        amenda[t][x] = cost;
    }

    for(int i = 0; i <= 3500; i++)
        for(int j = 1; j <= n; j++)
            dp[i][j] = -1;


    dp[0][1] = 0;
    for(int t = 1; t <= 3500; t++)
        for(int i = 1; i <= n; i++)
        {
            dp[t][i] = dp[t - 1][i];
            for(auto child : edges[i])
                if(t >= child.second)
                    dp[t][i] = max(dp[t][i], dp[t - child.second][child.first]);
            if(dp[t][i] != -1)
                dp[t][i] += amenda[t][i];
        }

    for(int i = 1; i <= p; i++)
    {
        int x, y;
        f >> x >> y;
        g << dp[y][x] << "\n";
    }

    return 0;
}