#include <iostream>
#include <fstream>
#include <cstring>
#include <algorithm>
#include <vector>

using namespace std;

#define maxN 155
#define maxT 3505
#define inf (1 << 30)
#define PB push_back
#define MKP make_pair
#define f first
#define s second

int DP[maxT][maxN], A[maxN][maxT];
vector < pair <int, int> > List[maxN];


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

    int N, M, K, P;
    f >> N >> M >> K >> P;

    while (M --)
    {
        int x, y, z;
        f >> x >> y >> z;

        List[x].PB ( MKP (y, z) );
        List[y].PB ( MKP (x, z) );
    }

    for (int i = 1; i <= K; ++ i)
    {
        int a, b, c;
        f >> a >> b >> c;

        A[a][b] = c;
    }

    for (int i = 0; i < maxT - 3; ++ i)
        for (int j = 1; j <= N; ++ j)
        {
            DP[i][j] = - inf;
            if (i == 0 && j == 1) DP[i][j] = 0;

            for (int t = 0; t < List[j].size(); ++ t)
            {
                int nod = List[j][t].f, tmp = List[j][t].s;

                if (i - tmp < 0) continue;

                DP[i][j] = max (DP[i][j], DP[i - tmp][nod]);
            }

            if (i - 1 >= 0) DP[i][j] = max (DP[i - 1][j], DP[i][j]);

            DP[i][j] += A[j][i];
        }

    while (P --)
    {
        int a, b;
        f >> a >> b;

        if (DP[b][a] < 0) g << "-1\n";
        else g << DP[b][a] << '\n';
    }

    return 0;
}