#include <bits/stdc++.h>
#define int long long
#define sqr(x) ((x) * (x))
using namespace std;
typedef pair<int, int> pi;
typedef pair<pi, int> ppi;
const int mod = 1e9+7;
const int inv_2 = (mod+1) / 2;
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
#ifdef LOCAL
freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
#endif
int k, n, m, o;
cin >> k >> n >> m >> o;
int p[n+1][k][18];
int toll[n+1][k][18];
fill(p[0][0], p[n+1][0], n);
memset(toll, 0x3f, sizeof(toll));
for(int i = 0; i < m; i++) {
int a, b, t;
cin >> a >> b >> t;
p[b][a%k][0] = a;
toll[b][a%k][0] = t;
}
for(int x = 1; x < 18; x++) {
for(int u = 0; u < n; u++) {
for(int i = 0; i < k; i++) {
int v = p[u][i][x-1];
for(int j = 0; j < k; j++) {
p[u][j][x] = min(p[u][j][x], p[v][j][x-1]);
toll[u][j][x] = min(toll[u][j][x], toll[u][i][x-1] + toll[v][j][x-1]);
}
}
}
}
while(o--) {
int a, b;
cin >> a >> b;
int delta = b / k - a / k;
int dis[k];
fill(dis, dis+k, 1e18);
dis[b % k] = 0;
int id = b / k;
for(int i = 0; i < 18; i++) {
if(delta & (1 << i)) {
int tmp[k];
fill(tmp, tmp+k, 1e18);
for(int j = 0; j < k; j++) {
for(int x = 0; x < k; x++) {
tmp[x] = min(tmp[x], dis[j] + toll[id*k+j][x][i]);
}
}
id -= (1 << i);
for(int j = 0; j < k; j++) {
dis[j] = tmp[j];
}
}
}
int ans = dis[a%k];
if(ans > 1e17)
cout << "-1\n";
else {
cout << ans << "\n";
}
}
}
