#include <bits/stdc++.h>
#define Nmax 155
#define Tmax 3505
#define DIM 70000
#define Pmax 8005

using namespace std;

class Ifstream{

private:
    FILE *fin;
    char *buffer;
    int cursor;
    char read_ch(){

        if(++cursor==DIM){

            cursor=0;
            fread(buffer,1,DIM,fin);
        }
        return buffer[cursor];
    }

public:
    Ifstream(const char *file_name){

        fin=fopen(file_name,"r");
        buffer=new char[DIM]();
        cursor=DIM-1;
    }

    Ifstream &operator >> (int &n){

        char c;
        n=0;
        while(!isdigit(c=read_ch()) and c!='-');
        int sgn=1;
        if(c=='-') sgn=-1;
        else n=c-'0';
        while(isdigit(c=read_ch()))
            n=10*n+c-'0';
        n*=sgn;
        return *this;
    }
};
class Ofstream{

private:
    FILE *fout;
    char *buffer;
    int cursor;
    void write_ch(char ch){

        if(cursor==DIM){

            fwrite(buffer,1,DIM,fout);
            cursor=0;
        }
        buffer[cursor++]=ch;
    }

public:
    Ofstream(const char *file_name){

        fout=fopen(file_name,"w");
        buffer=new char[DIM]();
        cursor=0;
    }

    ~Ofstream(){

        fwrite(buffer,1,cursor,fout);
        fclose(fout);
    }

    Ofstream &operator << (int n){

        if(n<0){

            write_ch('-');
            n=-n;
        }
        if(n<10) write_ch(n+'0');
        else{

            (*this)<<(n/10);
            write_ch(n%10+'0');
        }
        return *this;
    }

    Ofstream &operator << (char c){

        write_ch(c);
        return *this;
    }
};

Ifstream f("amenzi.in");
Ofstream g("amenzi.out");

int N,M,K,P,T;
list < pair <int,int> > G[Nmax];
pair <int,int> meeting[Pmax];

int dp[Nmax][Tmax];
int fine[Nmax][Tmax];

void read_data(){

    f>>N>>M>>K>>P;
    int x,y,z;
    while(M--){

        f>>x>>y>>z;
        G[x].push_back({y,z});
        G[y].push_back({x,z});
    }

    while(K--){

        f>>x>>y>>z;
        fine[x][y]+=z;
    }

    for(int i=1;i<=P;i++){

        f>>meeting[i].first>>meeting[i].second;
        T=max(T,meeting[i].second);
    }
}

void compute_dp(){

    for(int j,i=0;i<=N;i++)
        for(j=0;j<=T;j++)
            dp[i][j]=-1;

    dp[1][0]=fine[1][0];

    for(int node,t=0;t<=T;t++)
        for(node=1;node<=N;node++)
            if(dp[node][t]>-1){

                dp[node][t+1]=max(dp[node][t+1],dp[node][t]+fine[node][t+1]);
                for(const auto &it:G[node])
                    dp[it.first][t+it.second]=max(dp[it.first][t+it.second],dp[node][t]+fine[it.first][t+it.second]);
            }
}

void print_ans(){

    for(int i=1;i<=P;i++)
        g<<dp[meeting[i].first][meeting[i].second]<<'\n';
}

int main(){

    read_data();
    compute_dp();
    print_ans();

    return 0;
}