#include <bits/stdc++.h>

using namespace std;
ifstream in("amenzi.in");
ofstream out("amenzi.out");
const int N = 155;
const int T = 3505;
int dp[T][N],val[T][N];
bool viz[T][N];
vector< pair<int,int> > v[N];

int main()
{
    int n,m,k,p;
    in >> n >> m >> k >> p;
    for (int i = 1; i<=m; i++)
    {
        int x,y,c;
        in >> x >> y >> c;
        v[x].push_back({y,c});
        v[y].push_back({x,c});
    }
    for (int i = 1; i<=k; i++)
    {
        int a,b,c;
        in >> a >> b >> c;
        val[b][a] += c;
    }
    queue< pair<int,int> > q;
    for (int i = 0; i<=3500; i++)
        for (int j = 0; j<=n; j++)
            dp[i][j] = -1;
    dp[0][1] = val[0][1];
    for (int i = 1; i<=3500; i++)
        for (int j = 1; j<=n; j++)
        {
            dp[i][j] = dp[i-1][j];
            viz[i][j] = viz[i-1][j];
            for (auto it: v[j])
            {
                int next = it.first, c = it.second;
                if (i>=c)
                    dp[i][j] = max(dp[i][j],dp[i-c][next]);
            }
            if (dp[i][j]!=-1)
                dp[i][j]+=val[i][j];
        }
    for (int i = 1; i<=p; i++)
    {
        int x,y;
        in >> x >> y;
        out << dp[y][x] << "\n";
    }
}