#include <fstream>
#include <algorithm>
#include <cstring>
using namespace std;

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

const int MAXN = 155;
const int MAXK = 12005;
const int INF = 0x3f3f3f3f;
const int TMAX = 3505;
struct Amenda{
    int i, t, val;
};
int N, M, K, P;
int G[MAXN][MAXN];
int D[TMAX][MAXN];
int a[TMAX][MAXN];

void Read();
void DynamicProgramming();
void Answer();

bool Comp( const Amenda& a, const Amenda& b )
{
    return a.t <= b.t;
}

int main()
{
    Read();
    DynamicProgramming();
    Answer();

    fin.close();
    fout.close();
    return 0;
}

void Read()
{
    int i, x, y, c, t, val;

    memset( G, INF, sizeof(G) );
    fin >> N >> M >> K >> P;
    for ( i = 1; i <= M; i++ )
    {
        fin >> x >> y >> c;
        G[x][y] = G[y][x] = c;
    }

    for ( i = 1; i <= K; i++ )
    {
        fin >> x >> t >> val;
        a[t][x] += val;
    }
}

void DynamicProgramming()
{
    int i, j, k, t, ip;

    for ( i = 1; i <= N; i++ )
        G[i][i] = 0;

    for ( k = 1; k <= N; k++ )
        for ( i = 1; i <= N; i++ )
            for ( j = 1; j <= N; j++ )
                if ( i != j )
                    G[i][j] = min( G[i][j], G[i][k] + G[k][j] );

    memset(D, -1, sizeof(D));
    D[0][1] = 0;
    for ( t = 0; t < TMAX; t++ )
        for ( i = 1; i <= N; i++ )
        {
         //   if ( t == 6 && i == 5 )
          //      fout << "DA";

            if ( t == 0 && i == 1 ) continue;

            if ( t > 0 && D[t - 1][i] != -1 )
                D[t][i] = D[t - 1][i];

            for ( ip = 1; ip <= N; ip++ )
                if ( ip != i && G[i][ip] <= t && D[t - G[i][ip]][ip] + a[t][i] > D[t][i] && D[t - G[i][ip]][ip] != -1 )
                    D[t][i] = D[t - G[i][ip]][ip] + a[t][i];
        }
}

void Answer()
{
    int i, t, x;

    for ( i = 1; i <= P; i++ )
    {
        fin >> x >> t;

        fout << D[t][x] << '\n';
    }
}