#include <bits/stdc++.h>

using namespace std;

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

const int NMAX = 155;
const int PMAX = 8005;
const int KMAX = 12005;
const int TMAX = 3505;

int n,m,K,p;
long long mat[NMAX][TMAX], dp[NMAX][TMAX];
vector < pair < int, int > > v[NMAX];

int main(){
    int i,j,x,y,z;
    f >> n >> m >> K >> p;
    for(i = 1 ; i <= m ; i++){
        f >> x >> y >> z;
        v[x].push_back(make_pair(y,z));
        v[y].push_back(make_pair(x,z));
    }

    for(i = 1 ; i <= K ; i++){
        f >> x >> y >> z;
        mat[x][y] = z;
    }

    memset(dp, -1, sizeof(dp));

    dp[1][0] = mat[1][0];
    for(i = 1 ; i < TMAX ; i++)
        for(j = 1 ; j <= n ; j++){

            dp[j][i] = dp[j][i - 1];

            for(auto it: v[j]){

                if(i >= it.second)
                    dp[j][i] = max(dp[j][i], dp[it.first][i - it.second]);

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

    while(p--){
        f >> x >> y;
        g << dp[x][y] << "\n";
    }

    return 0;
}