#include<bits/stdc++.h>
#define pb push_back
#define mp make_pair
#define int long long
#define vi vector<int>
#define vvi vector<vector<int>>
#define pii pair<int, int>
#define vpii vector<pair<int, int>>
#define vc vector<char>
#define vb vector<bool>
#define mii map<int,int>
#define f0r(i,n) for(int i=0;i<n;i++)
#define FOR(i,k,n) for(int i=k;i<n;i++)
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
#define in(a) int a; cin>>a
#define in2(a,b) int a,b; cin>>a>>b
#define in3(a,b,c) int a,b,c; cin>>a>>b>>c
#define in4(a,b,c,d) int a,b,c,d; cin>>a>>b>>c>>d
#define vin(v,n); vi v(n); f0r(i,n){cin>>v[i];}
#define out(a) cout<<a<<'\n'
#define out2(a,b) cout<<a<<' '<<b<<'\n'
#define out3(a,b,c) cout<<a<<' '<<b<<' '<<c<<'\n'
#define out4(a,b,c,d) cout<<a<<' '<<b<<' '<<c<<' '<<d<<'\n'
#define pout(a) cout<<a.first<<' '<<a.second<<'\n'
#define vout(v) for(auto u : v){cout<<u<<' ';} cout<<'\n'
#define dout(a) cout<<a<<' '<<#a<<'\n'
#define dout2(a,b) cout<<a<<' '<<#a<<' '<<b<<' '<<#b<<'\n'
#define yn(x); if(x){cout<<"YES"<<'\n';}else{cout<<"NO"<<'\n';}
const int leg = 1e9 + 7;
const int mod = 998244353;
using namespace std;
const int mxn = 5e4 + 5;
vpii adj[mxn];
signed main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
//ifstream cin(".in");
//ofstream cout(".out");
in4(k,n,m,q);
f0r(i,m){
in3(a,b,w);
adj[a].pb(mp(b,w));
}
vector<vector<vector<int>>> jmp(n/k*k+k, vvi(k, vi(16, 1e12)));
f0r(i,n){
int nx = ((i/k) + 1) * k;
for(auto u : adj[i]){
jmp[i][u.first - nx][0] = u.second;
}
}
FOR(lg, 1, 16){
f0r(i, n){
f0r(j,k){
f0r(l,k){
int nxt = (1<<(lg-1)) * k + i/k*k + l;
if(nxt < n){
jmp[i][j][lg] = min(jmp[i][j][lg], jmp[i][l][lg-1] + jmp[nxt][j][lg-1]);
}
}
}
}
}
while(q--){
in2(a,b);
int la = a/k;
int lb = b/k;
if(la == lb)out(-1);
else{
vi cur;
f0r(i,k){
cur.pb(jmp[a][i][0]);
}
int jumps = lb - la - 1;
//dout(jumps);
//vout(cur);
int loc = la*k + k;
for(int i = 16; i>=0; i--){
if(jumps & (1 << i)){
vi nc(k,1e12);
f0r(j,k){
f0r(l,k){
nc[j] = min(nc[j], cur[l] + jmp[l + loc][j][i]);
}
}
loc += (1 << i) * k;
cur = nc;
}
}
int ans = cur[b%k];
if(ans == 1e12)out(-1);
else out(ans);
}
}
/*
if(k == -1){
vi v(n-1);
f0r(i,n-1){
if(adj[i].size() != 0)v[i] = adj[i][0].second;
else v[i] = 1e9;
}
vi ps(n);
FOR(i, 1, n){
ps[i] = ps[i-1] + v[i-1];
}
while(q--){
in2(a,b);
if(ps[b] - ps[a] < 1e9)cout<<ps[b] - ps[a]<<'\n';
else cout<<-1<<'\n';
}
}
else{
vvi dist(n, vi(k, 4e18));
for(int i = 0; i<n; i += k){
FOR(j, i, min(i+k,n)){
FOR(l, i+k, i+2*k){
if(l < n){
adj[j].pb({l,1e9});
}
}
}
}
f0r(kk,min(k,n)){
dist[kk][kk] = 0;
priority_queue<pii>pq;
pq.push({0,kk});
while(!pq.empty()){
int node = pq.top().second;
pq.pop();
for(auto u : adj[node]){
int nxt = u.first;
int w = u.second;
if(dist[nxt][kk] > dist[node][kk] + w){
dist[nxt][kk] = dist[node][kk] + w;
pq.push(mp(-dist[nxt][kk], nxt));
}
}
}
}
f0r(i,k){
f0r(j,n){
cout<<dist[j][i]<<' ';
}
cout<<'\n';
}
while(q--){
in2(a,b);
int mn = 4e18;
f0r(kk, min(k,n)){
if(dist[a][kk] != 4e18 && dist[b][kk] != 4e18){
mn = min(mn, dist[b][kk] - dist[a][kk]);
}
}
if(mn >= 1e9)out(-1);
else out(mn);
}
}
*/
}
