//Challenge: Accepted
#include <iostream>
#include <algorithm>
#include <utility>
#include <vector>
#define maxn 50005
#define int long long
using namespace std;
const int inf = (1<<30) - 1;
struct mat{
int m[5][5];
mat() {
for (int i = 0;i < 5;i++) {
for (int j = 0;j < 5;j++) m[i][j] = inf;
}
}
};
void print(mat a) {
for (int i = 0;i < 5;i++) {
for (int j = 0;j < 5;j++) cerr << a.m[i][j] << " ";
cerr << endl;
}
}
mat comb(mat a, mat b) {
mat ret;
for (int i = 0;i < 5;i++) {
for (int j = 0;j < 5;j++) {
ret.m[i][j] = inf;
for (int k = 0;k < 5;k++) ret.m[i][j] = min(ret.m[i][j], a.m[i][k] + b.m[k][j]);
}
}
return ret;
}
mat anc[16][maxn];
signed main() {
ios_base::sync_with_stdio(0);cin.tie(0);
int k, n, m, o;
cin >> k >> n >> m >> o;
for (int i = 0;i < m;i++) {
int a, b, t;
cin >> a >> b >> t;
anc[0][a / k].m[a % k][b % k] = t;
}
int len = (n + k - 1) / k;
for (int i = 1;i < 16;i++) {
for (int j = 0;j < len - (1<<i) + 1;j++) {
anc[i][j] = comb(anc[i - 1][j], anc[i - 1][j + (1<<(i - 1))]);
}
}
while (o--) {
int a, b;
cin >> a >> b;
int ai = a / k, bi = b / k;
mat cur;
for (int i = 0;i < 5;i++) {
cur.m[i][i] = 0;
}
for (int i = 15;i >= 0;i--) {
if (ai + (1<<i) <= bi) {
cur = comb(cur, anc[i][ai]);
ai += 1<<i;
}
}
int ans = cur.m[a % k][b % k];
cout << (ans >= inf ? -1 : ans) << "\n";
}
}
