#include <bits/stdc++.h>

using namespace std;

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

const int NMAX = 155;
const int TMAX = 3505;
int dp[TMAX][NMAX],val[TMAX][NMAX];
vector < pair < int, int > > v[NMAX];

int main()
{
    int n,m,k,p;
    f >> n >> m >> k >> p;
    for(int i = 1 ; i <= m ; i++)
    {
        int x,y,z;
        f >> x >> y >> z;
        v[x].push_back({y,z});
        v[y].push_back({x,z});
    }
    for(int i = 1 ; i <= k ; i++)
    {
        int x,y,z;
        f >> x >> y >> z;
        val[y][x] += z;
    }
    for(int i = 0 ; i <= 3500 ; i++)
        for(int j = 0 ; j <= n ; j++)
            dp[i][j] = -1;
    dp[0][1] = val[0][1];
    for(int i = 1 ; i <= 3500 ; i++)
        for(int j = 1 ; j <= n ; j++)
        {
            dp[i][j] = dp[i - 1][j];
            for(auto it: v[j])
            {
                int next = it.first, c = it.second;
                if(i >= c)
                    dp[i][j]= max(dp[i][j], dp[i - c][next]);
            }
            if(dp[i][j] != -1)
                dp[i][j] += val[i][j];
        }

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

    return 0;
}