#include <fstream>
#include <vector>
using namespace std;

ifstream fin("amenzi.in");
ofstream fout("amenzi.out");

const int MaxT = 3501, MaxN = 151;
int N, M, K, P;
vector<vector<pair<int, int>>> G;
int a[MaxN][MaxT], D[MaxN][MaxT];

void Read();

int main() {
    Read();
    for (int i = 0; i < MaxN; i++)
        for (int j = 0; j < MaxT; j++)
            D[i][j] = -1;
    D[1][0] = 0;
    for (int j = 0; j < MaxT; j++)
        for (int i = 1; i <= N; i++) {
            if (j != 0) D[i][j] = D[i][j - 1];
            for (const auto e : G[i])
                if (j >= e.second)
                    D[i][j] = max(D[i][j], D[e.first][j - e.second]);
            if (D[i][j] != -1) D[i][j] += a[i][j];
        }
    for (int i = 0, x, y; i < P; i++) {
        fin >> x >> y;
        fout << D[x][y] << '\n';
    }
    fin.close();
    fout.close();
    return 0;
}

void Read() {
    fin >> N >> M >> K >> P;
    G = vector<vector<pair<int, int>>>(N + 1);
    for (int i = 0, x, y, w; i < M; i++) {
        fin >> x >> y >> w;
        G[x].push_back({y, w});
        G[y].push_back({x, w});
    }
    for (int i = 0, x, y ,w; i < K; i++) {
        fin >> x >> y >> w;
        a[x][y] += w;
    }
}