#include <bits/stdc++.h>
#define INF 0x3f3f3f3f
using namespace std;
const int kN = 5e4;
const int kLog = 15;
const int kK = 5;
int res[kK][kK], ret[kK][kK], dp[kN][1 + kLog][kK][kK];
void minSelf(int &x, int y) {
if (y < x) {
x = y;
}
}
void combine(int n, int a[kK][kK], int b[kK][kK], int c[kK][kK]) {
for (int i = 0; i < n; ++i) {
for (int j = 0; j < n; ++j) {
for (int k = 0; k < n; ++k) {
minSelf(a[i][j], b[i][k] + c[k][j]);
}
}
}
}
void testCase() {
int k, n, m, q;
cin >> k >> n >> m >> q;
for (int i = 0; i <= (n - 1) / k; ++i) {
for (int j = 0; (1 << j) <= (n - 1) / k; ++j) {
for (int a = 0; a < k; ++a) {
for (int b = 0; b < k; ++b) {
dp[i][j][a][b] = INF;
}
}
}
}
for (int i = 0; i < m; ++i) {
int a, b, t;
cin >> a >> b >> t;
dp[a / k][0][a % k][b % k] = t;
}
for (int j = 1; (1 << j) <= (n - 1) / k; ++j) {
for (int i = 0; i + (1 << j) - 1 <= (n - 1) / k; ++i) {
combine(k, dp[i][j], dp[i][j - 1], dp[i + (1 << (j - 1))][j - 1]);
}
}
for (int qq = 0; qq < q; ++qq) {
int a, b;
cin >> a >> b;
if (a / k == b / k) {
cout << "-1\n";
continue;
}
for (int i = 0; i < k; ++i) {
for (int j = 0; j < k; ++j) {
if (i == j) {
res[i][i] = 0;
} else {
res[i][j] = INF;
}
}
}
int s = a / k, t = b / k;
for (int i = kLog; i >= 0; --i) {
if (s + (1 << i) <= t) {
for (int l = 0; l < k; ++l) {
for (int c = 0; c < k; ++c) {
ret[l][c] = res[l][c];
res[l][c] = INF;
}
}
combine(k, res, ret, dp[s][i]);
s += (1 << i);
}
}
if (res[a % k][b % k] == INF) {
cout << "-1\n";
} else {
cout << res[a % k][b % k] << '\n';
}
}
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int tests = 1;
for (int tc = 0; tc < tests; ++tc) {
testCase();
}
return 0;
}
