#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
#define all(a) (a).begin(), (a).end()
#define replr(i, a, b) for (int i = int(a); i <= int(b); ++i)
#define reprl(i, a, b) for (int i = int(a); i >= int(b); --i)
#define rep(i, n) for (int i = 0; i < int(n); ++i)
#define mkp(a, b) make_pair(a, b)
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<PII> VPI;
typedef vector<VI> VVI;
typedef vector<VVI> VVVI;
typedef vector<VPI> VVPI;
typedef pair<ll, ll> PLL;
typedef vector<ll> VL;
typedef vector<PLL> VPL;
typedef vector<VL> VVL;
typedef vector<VVL> VVVL;
typedef vector<VPL> VVPL;
template<class T> T setmax(T& a, T b) {if (a < b) return a = b; return a;}
template<class T> T setmin(T& a, T b) {if (a < b) return a; return a = b;}
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
template<class T>
using indset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
void solve() {
int K, n, m, q;
cin >> K >> n >> m >> q;
VVVL dist(n, VVL(20, VL(K, 1e18)));
rep(i, m) {
ll u, v, w;
cin >> u >> v >> w;
setmin(dist[u][0][v%K], w);
}
for (int i = 1; i < 20; i++) rep(u, n) {
int tmp1 = (u/K + (1<<(i-1)))*K;
int tmp2 = (u/K + (1<<i))*K;
replr(m, tmp1, min(n-1, tmp1+K-1)) replr(f, tmp2, min(n-1, tmp2+K-1)) setmin(dist[u][i][f%K], dist[u][i-1][m%K] + dist[m][i-1][f%K]);
}
while (q--) {
int u, v;
cin >> u >> v;
int d = v/K - u/K;
VL a(K, 1e18);
a[u%K] = 0;
u = u/K*K;
for (int i = 0; i < 20; i++) if (d & (1<<i)) {
VL b(K, 1e18);
replr(s, u, min(n-1, u+K-1)) rep(f, K) {
setmin(b[f], a[s%K] + dist[s][i][f]);
}
a = b;
u += (1<<i)*K;
}
ll ans = a[v%K];
if (ans == 1e18) cout << -1 << endl;
else cout << ans << endl;
}
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
int t = 1;
/* cin >> t; */
while (t--) solve();
}
