// Source: https://usaco.guide/general/io
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define eb emplace_back // faster than push_back xD
// pbds UwU
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
#define oset tree<ll, null_type,less<ll>, rb_tree_tag,tree_order_statistics_node_update> // use pair for ms
// my io library :D
#define m1(x) template<class T, class... U> void x(T&& a, U&&... b)
#define m2(x) (ll[]){(x forward<U>(b),0)...}
m1(pr){cout << forward<T>(a); m2(cout << " " <<); cout << "\n";}
m1(re){cin >> forward<T>(a); m2(cin >>);}
const ll cap = 5e4+1;
ll dist[cap];
vector<pair<ll,ll>> adj[cap];
/*
void dijkstra(ll s){
priority_queue<pair<ll,ll>> pq;
fill(dist, dist+cap, 1e18);
pq.push({0, s});
dist[s] = 0;
while (!pq.empty()){
pair<ll,ll> oknext = pq.top(); pq.pop();
oknext.first *= -1;
for (auto u: adj[oknext.second]){
if (dist[oknext.second] + u.second < dist[u.first]){
dist[u.first] = dist[oknext.second] + u.second;
pq.push({-dist[u.first], u.first});
}
}
}
}
*/
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
ll k, n, m, o;
re(k, n, m, o);
vector<ll> w(n, -1);
for (ll i{}; i < m; i++){
ll a, b, t; re(a, b, t);
adj[a].eb(make_pair(b, t));
if (b == a + 1) {
if (w[a] == -1) w[a] = t;
else w[a] = min(w[a], t);
}
}
vector<ll> comp(n, -1);
ll cid = 0;
for (ll i = 0; i < n; i++) {
if (i == 0 || w[i-1] == -1) cid++;
comp[i] = cid;
}
vector<ll> pref(n, 0);
for (ll i = 1; i < n; i++){
if (w[i] == -1) pref[i] = 0;
else pref[i] = pref[i-1] + w[i-1];
}
for (ll i{}; i < o; i++){
ll a, b; re(a, b);
if (comp[a] != comp[b]) pr(-1);
else pr(pref[b] - pref[a]);
}
}
