# include <fstream>
# include <algorithm>
# include <vector>
# define Tmax 3505
# define N 155
using namespace std;
ifstream f("amenzi.in");
ofstream g("amenzi.out");
struct elem2
{
    int a, b;
}var[8005];
struct elem
{
    int x, y, cost;
}v[1505];
int i,j,n,m,K,p,x,y,a,b,c,t,cost,maxx;
int mat[N][Tmax], amenda[N][Tmax];
int main ()
{
    f>>n>>m>>K>>p;
    for (i=1; i<=m; ++i)
        f>>v[i].x>>v[i].y>>v[i].cost;

    for (i=1; i<=K; ++i)
    {
        f>>a>>b>>c;
        amenda[a][b]=+c; //intersectia a la momentul b
    }

    for (i=1; i<=p; ++i)
    {
        f>>var[i].a>>var[i].b;
        maxx=max(maxx, var[i].b);
    }


    mat[1][0]=1;
    for (t=1; t<=maxx; ++t)
    {
        for (i=1; i<=m; ++i)
        {
            x=v[i].x; y=v[i].y; cost=v[i].cost;
            mat[x][t]=max(mat[x][t], mat[x][t-1]);
            mat[y][t]=max(mat[y][t], mat[y][t-1]);
            if (cost<=t)
            {
                //de la x la y
                mat[x][t]=max(mat[x][t], mat[y][t-cost]);

                //de la t la x
                mat[y][t]=max(mat[y][t], mat[x][t-cost]);
            }
        }
        for (i=1; i<=n; ++i)
        {
            if (mat[i][t]) mat[i][t]+=amenda[i][t];
        }
    }

    for (i=1; i<=p; ++i)
    {
        a=var[i].a; b=var[i].b;
        if (mat[a][b]) g<<mat[a][b]-1<<"\n";
                  else g<<"-1\n";
    }

    return 0;
}