#include <bits/stdc++.h>
#define maxN 155
#define maxT 3505
#define INF (1<<30)
using namespace std;
vector<pair<int,int> >v[maxN];
int n,i,j,k,p,t,m,r,x,y,z;
int cost[maxN][maxT];
int dp[maxN][maxT];
int main()
{
    freopen("amenzi.in","r",stdin);
    freopen("amenzi.out","w",stdout);
    scanf("%d %d %d %d",&n,&m,&k,&p);
    for(i=1;i<=m;i++)
        scanf("%d %d %d",&x,&y,&z),
        v[x].push_back(make_pair(y,z)),
        v[y].push_back(make_pair(x,z));
    for(i=1;i<=k;i++)
        scanf("%d %d %d",&x,&y,&z),
        cost[x][y]+=z;
    for(i=1;i<=n;i++)
        dp[i][0]=-INF;
    dp[1][0]=cost[1][0];
    for(j=1;j<=3500;j++)
        for(i=1;i<=n;i++)
        {
            dp[i][j]=dp[i][j-1]+cost[i][j];
            for(vector<pair<int,int> >::iterator it=v[i].begin();it!=v[i].end();it++)
                if((it->second)<=j)
                    dp[i][j]=max(dp[i][j],dp[it->first][j-(it->second)]+cost[i][j]);
        }
    for(i=1;i<=p;i++)
    {
        scanf("%d %d",&x,&y);
        if(dp[x][y]<0)
            printf("-1\n");
        else printf("%d\n",dp[x][y]);
    }
    return 0;
}