#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;
struct Amenda{
    int i, t, val;
};
int N, M, K, P;
int G[MAXN][MAXN];
int D[MAXK];
Amenda a[MAXK];

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;

    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 >> a[i].i >> a[i].t >> a[i].val;
    sort(a + 1, a + 1 + K, Comp);
}

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

    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] );

    D[0] = 0;
    for ( i = 1; i <= K; i++ )
    {
        if ( G[1][a[i].i] <= a[i].t )
            D[i] = a[i].val;

        for ( j = 1; j < i; j++ )
            if ( a[j].t + G[a[j].i][a[i].i] <= a[i].t && D[j] + a[i].val > D[i] )
                D[i] = D[j] + a[i].val;
    }
}

void Answer()
{
    int i, t, x, rez = 0, j;

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

        if ( G[1][x] > t )
            rez = -1;
        else
            rez = 0;

        for ( j = 1; j <= K; j++ )
            if ( G[a[j].i][x] + a[j].t <= t && D[j] > rez )
                rez = D[j];

        fout << rez << '\n';
    }
}