#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define FOR(i, a, b) for(ll i = (ll)a; i <= (ll)b; i++)
#define DEC(i, a, b) for(ll i = (ll)a; i >= (ll)b; i--)
typedef pair<ll, ll> pi;
typedef pair<pi, ll> pii;
typedef pair<ll, pi> ipi;
typedef pair<pi, pi> pipi;
#define f first
#define s second
typedef vector<ll> vi;
typedef vector<pi> vpi;
typedef vector<pii> vpii;
#define pb push_back
#define pf push_front
#define all(v) v.begin(), v.end()
#define size(v) (ll) v.size()
#define disc(v) sort(all(v)); v.resize(unique(all(v)) - v.begin());
#define INF (ll) 1e9 + 100
#define LLINF (ll) 1e11
#define fastio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define sandybridge __attribute__((optimize("Ofast"), target("arch=sandybridge")))
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count()); //can be used by calling rng() or shuffle(A, A+n, rng)
inline ll rand(ll x, ll y) { ++y; return (rng() % (y-x)) + x; } //inclusivesss
ll k, n, m, q, a, b, c, dist[50005][17][5][5], p[50005][17];
int main() {
fastio; cin >> k >> n >> m >> q;
n += k - (n % k);
FOR(i, 0, n/k-1) FOR(t, 0, 16) FOR(j, 0, k-1) FOR(l, 0, k-1) dist[i][t][j][l] = LLINF;
memset(p, -1, sizeof p);
FOR(i, 1, m) {
cin >> a >> b >> c;
dist[a/k][0][a%k][b%k] = c;
}
FOR(i, 0, n/k-2) p[i][0] = i+1;
FOR(t, 1, 16) DEC(i, n/k-2, 0) if (p[i][t-1] != -1) p[i][t] = p[p[i][t-1]][t-1];
DEC(i, n/k-1, 0) FOR(t, 1, 16) if (p[i][t] != -1) {
FOR(x, 0, k-1) FOR(z, 0, k-1) FOR(y, 0, k-1) dist[i][t][x][z] = min(dist[i][t][x][z], dist[i][t-1][x][y] + dist[p[i][t-1]][t-1][y][z]);
}
while (q--) {
cin >> a >> b;
ll x = a/k;
vi pos; FOR(i, 0, k-1) pos.pb((i == a%k ? 0 : LLINF));
DEC(t, 16, 0) if (p[x][t] != -1 and p[x][t] <= b/k) {
vi newpos(k, LLINF);
FOR(i, 0, k-1) FOR(y, 0, k-1) newpos[y] = min(newpos[y], dist[x][t][i][y] + pos[i]);
pos = newpos;
x = p[x][t];
}
cout << (pos[b%k] == LLINF ? -1 : pos[b%k]) << "\n";
}
}
