#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[maxT][maxN];
int dp[maxT][maxN];
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[y][x]+=z;
    memset(dp,-1,sizeof(dp));
    dp[0][1]=0;
    for(i=1;i<=3500;i++)
        for(j=1;j<=n;j++)
        {
            for(vector<pair<int,int> >::iterator it=v[j].begin();it!=v[j].end();it++)
                if((it->second)<=i)
                    dp[i][j]=max(dp[i][j],dp[i-(it->second)][it->first]);
            dp[i][j]=max(dp[i][j],dp[i-1][j]);
            if(dp[i][j]>=0)
                dp[i][j]+=cost[i][j];
        }
    for(i=1;i<=p;i++)
    {
        scanf("%d %d",&x,&y);
        printf("%d\n",dp[y][x]);
    }
    return 0;
}