#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define N 400005
#define ff first
#define ss second
#define pb push_back
#define sz(s) (int)s.size()
#define rep(c, a, b) for(c = a; c <= b; c++)
ll n, m, K, p[N], o, par[N];
vector <pair<int,int>> v[N];
int main () {
ios::sync_with_stdio(0);cin.tie(0);
cin >> K >> n >> m >> o;
for(int i = 1; i <= m; i++) {
int x, y, t;
cin >> x >> y >> t;
x++;
y++;
v[x].pb({y,t});
par[x] = y;
}
for(int i = 1; i <= n; i++) {
if(!sz(v[i])) continue;
p[i] = p[i - 1];
p[i] += v[i][0].ss;
}
for(int i = 1; i <= o; i++) {
int x, y;
cin >> x >> y;
x++;
y++;
int l = x;
while(par[l] != 0) {
if(l == y) break;
l = par[l];
}
if(l!=y) {
cout << "-1\n";
continue;;
}
cout << p[y - 1] - p[x - 1] << '\n';
}
}
