#include <fstream>
#include <vector>
using namespace std;
ifstream f("amenzi.in");
ofstream g("amenzi.out");
int N,M,K,P;
vector <int> G[155];
vector <int> Cost[155];
int cost[155][3505],DP[155][3505];
void Read()
{
    int i;
    f>>N>>M>>K>>P;
    for(i=1;i<=M;i++)
    {
        int x,y,c;
        f>>x>>y>>c;
        G[x].push_back(y);
        G[y].push_back(x);
        Cost[x].push_back(c);
        Cost[y].push_back(c);
    }
    for(int i=1;i<=K;i++)
    {
        int point,c,time;
        f>>point>>time>>c;
        cost[point][time]+=c;
    }
}

void DFS(int node,int time,int father,int c)
{
    if(time>3500)
        return;
    bool ok=0;
    if(node==1 && father==0 && time==0)
        ok=1;
    while(ok==0)
    {
        DP[node][time]=max(DP[father][time-c]+cost[node][time],DP[node][time]);
        DP[node][time]=max(DP[node][time-1],DP[node][time]);
        ok=1;
    }

    for(int i=0;i<G[node].size();i++)
    {
        int neighbour=G[node][i];
        int c=Cost[node][i];
        DFS(neighbour,time+c,node,c);
    }
}
void Browse()
{
    for(int i=1;i<=N;i++)
        for(int j=0;j<=3500;j++)
            DP[i][j]=-1;
    DP[1][0]=0;
   for(int i=0;i<=3500;i++)
    for(int j=1;j<=N;j++)
    {
        if(i>0)
            DP[j][i]=DP[j][i-1];
        for(int k=0;k<G[j].size();k++)
        {
            int neigh=G[j][k];
            int c=Cost[j][k];
            if(i>=c)
                DP[j][i]=max(DP[neigh][i-c],DP[j][i]);
        }
        if(DP[j][i]!=-1)
            DP[j][i]+=cost[j][i];
    }
    for(int i=1;i<=P;i++)
    {
        int x,y;
        f>>x>>y;
        DP[x][y]=max(DP[x][y],0);
        g<<DP[x][y]<<"\n";
    }
}
int main()
{
    Read();
    Browse();
    return 0;
}