#include <cstdio>
#include <vector>

#define NMAX 151
#define TMAX 3501

struct Edge {
    int node, cost;
    Edge(int node, int cost) {
        this->node = node;
        this->cost = cost;
    }
};

int n, m;
std::vector<Edge> ad[NMAX];

int k;
int ev[NMAX][TMAX];

int p;
int dp[NMAX][TMAX];

inline int max(int x, int y) {
    return x > y ? x : y;
}

int main() {
    freopen("amenzi.in", "r", stdin);
    freopen("amenzi.out", "w", stdout);

    int x, y, z;
    scanf("%d %d %d %d\n", &n, &m, &k, &p);

    for (int i = 0; i < m; i++) {
        scanf("%d %d %d\n", &x, &y, &z);
        ad[x].push_back(Edge(y, z));
        ad[y].push_back(Edge(x, z));
    }

    for (int i = 0; i < k; i++) {
        scanf("%d %d %d\n", &x, &y, &z);
        ev[x][y] += z;
    }

    for (int i = 2; i <= n; i++)
        dp[i][0] = -1;

    for (int j = 1; j < TMAX; j++)
        for (int i = 1; i <= n; i++) {
            dp[i][j] = dp[i][j - 1];
            for (Edge edge : ad[i])
                if (j >= edge.cost)
                    dp[i][j] = max(dp[i][j], dp[edge.node][j - edge.cost]);

            if (dp[i][j] != -1)
                dp[i][j] += ev[i][j];
        }

    for (int i = 0; i < p; i++) {
        scanf("%d %d\n", &x, &y);
        if (dp[x][y] == -1)
            printf("-1\n");
        else
            printf("%d\n", dp[x][y]);
    }

    fclose(stdout);
    return 0;
}