#include <iostream>
#include <cstdio>
#include <string>
#include <queue>

using namespace std;
int amenda[154][3504], ma[154][3504];
vector < pair<int,int> > g[154];
vector < pair<int,int> > sotie;
int n,m,k,p,a,b,c,pm,l;
int main()
{
    freopen("amenzi.in","r",stdin);
    freopen("amenzi.out","w",stdout);
    scanf("%d %d %d %d", &n,&m,&k,&p);
    for(int i=0;i<m;i++)
    {
        scanf("\n%d %d %d", &a,&b,&c);
        g[a].push_back(make_pair(b,c));
        g[b].push_back(make_pair(a,c));
    }
    for(int i=0;i<k;i++)
    {
        scanf("\n%d %d %d", &a,&b,&c);
        amenda[a][b]+=c;
    }
    for(int i=0;i<p;i++)
    {
        scanf("\n%d %d", &a,&b);
        sotie.push_back(make_pair(a,b));
        pm=max(pm,b);
    }
    for(int i=1;i<=n;i++)
    {
        for(int j=0;j<=pm;j++)
            ma[i][j]=-1;
    }
    ma[1][0]=0;
    for(int timp=1;timp<=pm;++timp)
    {
        for(int nod=1;nod<=n;++nod)
        {
            l=g[nod].size();
            for(int i=0;i<l;++i)
                if(timp-g[nod][i].second>=0)
                    ma[nod][timp]=max(ma[nod][timp],ma[g[nod][i].first][timp-g[nod][i].second]);
            ma[nod][timp]=max(ma[nod][timp],ma[nod][timp-1]);
            if(ma[nod][timp]!=-1)
                ma[nod][timp]+=amenda[nod][timp];
        }
    }
    for(int i=0;i<p;i++)
        cout<<ma[sotie[i].first][sotie[i].second]<<"\n";
    return 0;
}