#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ii pair<int, int>
const int N = 1e6 + 5;
int upf[N][18][5];
int d[N];
vector<ii> a[N];
bool vis[N];
int k, n, m, o;
void bfs() {
for (int u = n; u >= 0; u--) {
for (auto P : a[u]) {
upf[u][0][P.first % k] = min(upf[u][0][P.first % k], P.second);
}
for (int g = 1; g < 16; g++) {
for (int j = 0; j < k; j++) {
for (int p = 0; p < k; p++) {
int nodep = (u / k + (1 << (g-1))) * k + p;
upf[u][g][j] = min(upf[u][g][j], upf[u][g-1][p] + upf[nodep][g-1][j]);
}
}
}
}
}
inline int jump(pair<int, int> x, pair<int, int> y) {
int z = y.first - x.first;
int currb[5] = {(int)1e16, (int)1e16, (int)1e16, (int)1e16, (int)1e16};
currb[x.second] = 0;
int floor = x.first;
for (int j = 0; (1 << j) <= z; j++) {
if ((z >> j) & 1) {
int curr[5] = {(int)1e16, (int)1e16, (int)1e16, (int)1e16, (int)1e16};
for (int p = 0; p < k; p++) {
for (int y = 0; y < k; y++) {
curr[p] = min(curr[p], currb[y] + upf[floor*k+y][j][p]);
}
}
floor += (1 << j);
swap(curr, currb);
}
}
return currb[y.second];
}
int query(int u, int v) {
int x = jump({u / k, u % k}, {v / k, v % k});
return x;
}
signed main() {
if (fopen("D.inp", "r")) {
freopen("D.inp", "r", stdin);
freopen("D.out", "w", stdout);
}
cin.tie(0)->sync_with_stdio(false);
cin >> k >> n >> m >> o;
for (int i = 0; i <= n; i++) {
for (int j = 0; j < 20; j++) {
for (int x = 0; x < k; x++) {
upf[i][j][x] = 1e16;
// up[i][j][x] = -1;
}
}
}
for (int i = 1; i <= m; i++){
int u, v, w;
cin >> u >> v >> w;
a[u].push_back({v, w});
}
bfs();
while (o--) {
int u, v;
cin >> u >> v;
if (u / k > v/k || (u / k == v / k && u != v)) {
cout << "-1\n";
continue;
}
int x = query(u, v);
if (x >= 1e16) cout << "-1\n";
else cout << x << '\n';
}
return 0;
}
