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

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

const int DimT = 3505, DimN = 155;

vector<vector<pair<int, int>>> G;

int d[DimN][DimT], a[DimN][DimT];
int n,m,k,p;

void Read();

void Solve();
void Write();

int main()
{
    Read();
    Solve();
    Write();
}

void Read()
{
    fin >> n >> m >> k >> p;
    G = vector<vector<pair<int, int>>>(n + 1, vector<pair<int, int>>());
    int x, y, c;
    for (int i = 1; i <= m; i++)
    {
        fin >> x >> y >> c;
        G[x].push_back(make_pair(y,c));
        G[y].push_back(make_pair(x,c));
    }

    for( int i = 1; i <= k; i++)
    {
        fin >> x >> y >> c;
        a[x][y] += c;
    }
}

void Solve()
{

    for (int i = 0; i < DimN; i++)
        for (int j = 0; j < DimT; j++)
            d[i][j]=-1;
    d[1][0]=0;

    for (int i = 0; i < DimT; i++)
        for (int j = 1; j <= n; j++)
        {
            if( i > 0 )
                d[j][i] = d[j][i-1];
            for ( auto x : G[j] )
                if ( i >= x.second )
                    d[j][i]= max(d[j][i], d[x.first][i-x.second]);
            if ( d[j][i] != -1)
                d[j][i] += a[j][i];
        }
}

void Write()
{
    int x, y;
    for(int i = 1; i <= p; i++)
    {
        fin >> x >> y;
        fout << d[x][y] << "\n";
    }
}