#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <cstring>
#include <utility>
#include <vector>
#define tmax 3500
using namespace std;
int n,m,k,p,c[tmax+2][152],dp[tmax+2][152];
vector<pair<int,int> > v[152];
int main()
{
    int x,y,z;
    freopen("amenzi.in","r",stdin);
    freopen("amenzi.out","w",stdout);
    scanf("%d %d %d %d",&n,&m,&k,&p);
    memset(dp,-1,sizeof(dp));
    for (int 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(int i=1;i<=k;i++)
    {
        scanf("%d %d %d",&x,&y,&z);
        c[y][x]+=z;
    }
    dp[0][1]=0;
    for(int i=1;i<=tmax;i++)
       {

        for(int nod=1;nod<=n;nod++)
    {
        for(int j=0;j<v[nod].size();j++)
            if(i-v[nod][j].second>=0)
                dp[i][nod]=max(dp[i][nod],dp[i-v[nod][j].second][v[nod][j].first]);

            if(dp[i-1][nod]>dp[i][nod])
                dp[i][nod]=dp[i-1][nod];
            if(dp[i][nod]>=0)
                dp[i][nod]+=c[i][nod];
    }}
    for(int i=1;i<=p;i++)
    {
        scanf("%d %d",&x,&y);
        printf("%d\n",dp[y][x]);
    }
    fclose(stdin);
    fclose(stdout);

    return 0;
}