#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 5e4 + 7;
const ll INF = 1e18;
int k, n, m, o;
struct Matrix {
ll mat[5][5];
Matrix() {
for (int x = 0; x < 5; ++x) {
for (int y = 0; y < 5; ++y) {
mat[x][y] = INF;
}
}
}
Matrix operator * (Matrix other) {
Matrix c;
for (int x = 0; x < k; ++x) {
for (int y = 0; y < k; ++y) {
for (int z = 0; z < k; ++z) {
c.mat[x][y] = min(c.mat[x][y], mat[x][z] + other.mat[z][y]);
}
}
}
return c;
}
};
Matrix dist[N][17];
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cin >> k >> n >> m >> o;
while (m--) {
int a, b, t;
cin >> a >> b >> t;
dist[a / k][0].mat[a % k][b % k] = t;
}
int layers = (n + k - 1) / k;
for (int j = 1; j < 17; ++j) {
for (int i = 0; i + (1 << j) < layers; ++i) {
dist[i][j] = dist[i][j - 1] * dist[i + (1 << (j - 1))][j - 1];;
}
}
while (o--) {
int a, b;
cin >> a >> b;
Matrix ans;
for (int i = 0; i < 5; ++i) {
ans.mat[i][i] = 0;
}
int cur = a / k;
for (int i = 16; i >= 0; --i) {
if (cur + (1 << i) <= b / k) {
ans = ans * dist[cur][i];
cur += (1 << i);
}
}
cout << (ans.mat[a % k][b % k] == INF ? -1 : ans.mat[a % k][b % k]) << "\n";
}
return 0;
}
