#include <bits/stdc++.h>
#define pii pair<int, int>
///N=150
///M=1500
///T=3500
using namespace std;
int n, m, k, p, i, j, t=-1;
int sol[151][3501], costs[151][3501];
vector<pii> graph[151];
pii pairs[8001];
///
void read();
void solve();
void write();
int main()
{
    read();
    solve();
    write();
    return 0;
}
void read(){
    freopen("amenzi.in", "r", stdin);
    scanf("%d%d%d%d", &n, &m, &k, &p);
    for(i=1; i<=m; ++i){
        int x, y, c;
        scanf("%d%d%d", &x, &y, &c);
        graph[x].push_back({y, c});
        graph[y].push_back({x, c});
    }
    for(i=1; i<=k; ++i){
        int x, y, c;
        scanf("%d%d%d", &x, &y, &c);
        costs[x][y]=c;
    }
    for(i=1; i<=p; ++i){
        int x, y;
        scanf("%d%d", &x, &y);
        t=max(t, y);
        pairs[i]={x, y};
    }
    fclose(stdin);
}
void solve(){
    sol[1][0]=1;
    for(i=1; i<=t; ++i){
        for(j=1; j<=n; ++j){
            sol[j][i]=sol[j][i-1];
            for(auto next:graph[j]) {
                if(i-next.second<0) continue;
                sol[j][i]=max(sol[j][i], sol[next.first][i-next.second]);
            }
            if(sol[j][i]) sol[j][i]+=costs[j][i];
        }
    }
}
void write(){
    freopen("amenzi.out", "w", stdout);
    for(i=1; i<=p; ++i) printf("%d\n", sol[pairs[i].first][pairs[i].second]-1);
    fclose(stdout);
}