#include <cmath>
#include <iostream>
#include <set>
#include <climits>
#include <cstdio>
#include <algorithm>
#include <cassert>
#include <string>
#include <vector>
#include <iomanip>
#include <unordered_map>
#include <type_traits>
#include <string>
#include <queue>
#define ll long long
#include <map>
using namespace std;
int64_t dp[50050][32][5][5];
int K, N, M, O;
vector<vector<int64_t>> f (int in1, int in2) {
vector<vector<int64_t>> cur(K);
for (int i = 0; i < K; i++) {
cur[i].assign(K, INT_MAX);
cur[i][i] = 0;
}
int dif = abs(in1 - in2);
while (dif > 0) {
vector<vector<int64_t>> new_cur = cur;
for (int i = 0; i < K; i++) {
new_cur[i].assign(K, INT_MAX);
}
int lg2 = log2(dif);
for (int i = 0; i < K; i++) {
for (int j = 0; j < K; j++) {
for (int k = 0; k < K; k++) {
new_cur[i][j] = min(new_cur[i][j], cur[i][k] + dp[in1][lg2][k][j]);
}
}
}
dif -= (1 << lg2);
in1 += (1 << lg2);
cur = new_cur;
}
return cur;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> K >> N >> M >> O;
N++;
while (N % K != K - 1) {
N++;
}
for (int j = 0; j < 32; j++) {
for (int i = 0; i < N/K; i++) {
for (int x = 0; x < K; x++) {
for (int y = 0; y < K; y++) {
dp[i][j][x][y] = INT_MAX;
}
}
}
}
while (M--) {
int64_t a, b, w;
cin >> a >> b >> w;
dp[a/K][0][a % K][b % K] = min(w, dp[a/K][0][a % K][b % K]);
}
for (int j = 1; j < 32; j++) {
for (int i = 0; i < N/K; i++) {
for (int x = 0; x < K; x++) {
for (int y = 0; y < K; y++) {
for (int z = 0; z < K; z++) {
if (i + (1 << (j - 1)) < N/K)
dp[i][j][x][y] = min(dp[i][j][x][y], dp[i][j - 1][x][z] + dp[i + (1 << (j - 1))][j - 1][z][y]);
}
}
}
}
}
while (O--) {
int a, b;
cin >> a >> b;
if (a/K == b/K) {
cout << "-1\n";
continue;
}
vector<vector<int64_t>> vec = f(a/K, b/K);
if (vec[a % K][b % K] == INT_MAX) {
cout << "-1\n";
continue;
}
cout << vec[a % K][b % K] << '\n';
}
}
