#include<fstream>
#include<vector>

using namespace std;
ifstream f("amenzi.in");
ofstream g("amenzi.out");
int x,y,i,j,k,n,m,p,s,c,d[3510][155],a[3510][155];
struct nod{int x,t;};
nod nou;
vector<nod>l[155];
/*
inline void afis(int k, nod t)
{
    for(int i = 1; i <= n; i++)
        fout << d[i][k] << " " << a[k][i] << "\n";

    k = 0;

    while(k == 0)
    {
        i++;
        a[i][2*i] = d[i][2*i];

        if(a[i][2*i] == a[2*i][i])
            k = 1;
    }

    if(k < 0)
        return;

}


*/

int main()
{
    f>>n>>m>>k>>p;
    for(i=1;i<=m;++i)
    {
        f>>x>>y>>c;
        nou.x=x;
        nou.t=c;
        l[y].push_back(nou);
        nou.x=y;
        l[x].push_back(nou);
    }
    for(i=1;i<=k;++i)
    {
        f>>x>>y>>s;
        a[y][x]+=s;
    }
    d[0][1]=1;
    for(i=1;i<=3500;++i)
    {
        for(j=1;j<=n;++j)
        {
            d[i][j]=d[i-1][j];
            for(k=0;k<l[j].size();++k)
            if(i>=l[j][k].t&&d[i-l[j][k].t][l[j][k].x]>d[i][j])
            {
                d[i][j]=d[i-l[j][k].t][l[j][k].x];
            }
            if(d[i][j])
            d[i][j]+=a[i][j];
        }
    }
    for(i=1;i<=p;++i)
    {
        f>>x>>y;
        g<<(d[y][x]-1)<<'\n';
    }
    return 0;
}