#include<bits/stdc++.h>
#define pb push_back
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;

const int maxn=256;
const int mod=1e9+7;

ifstream fin;
ofstream fout;

int n, m, k, p;

int a, b, c;
vector<pii> nbrs[maxn];
ll crimes[maxn][3505];

ll dp[maxn][3505]; ///max money to be at vertex i at time j

int main(){

fin.open("amenzi.in");
fout.open("amenzi.out");

ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);

fin>>n>>m>>k>>p;

for(int i=0; i<m; i++){
    fin>>a>>b>>c;
    nbrs[a].pb({b, c});
    nbrs[b].pb({a, c});
}

for(int i=0; i<=n; i++){
    for(int j=0; j<=3503; j++){
        crimes[i][j]=0;
    }
}

for(int i=0; i<k; i++){
    fin>>a>>b>>c;
    crimes[a][b]+=c;
}

for(int i=0; i<=n; i++){
    for(int j=0; j<=3503; j++){
        dp[i][j]=-1;
    }
}

dp[1][0]=crimes[1][0];

for(int j=1; j<=3503; j++){
    for(int i=1; i<=n; i++){
        dp[i][j]=dp[i][j-1];

        for(auto x: nbrs[i]){
            int v=x.first;
            int dist=x.second;

            if(j>=dist){
                //cerr<<"I can get to "<<i<<" from "<<v<<" where i was at "<<j-dist<<" to time "<<j<<endl;
                dp[i][j]=max(dp[i][j], dp[v][j-dist]);
            }
        }

        if(dp[i][j]!=-1){
            dp[i][j]+=crimes[i][j];
        }
    }
}

for(int i=0; i<p; i++){
    fin>>a>>b;
    fout<<dp[a][b]<<endl;
}

return 0;
}