// Source: https://usaco.guide/general/io #include <bits/stdc++.h> using namespace std; using ll = long long; #define eb emplace_back // faster than push_back xD // pbds UwU #include <ext/pb_ds/assoc_container.hpp> using namespace __gnu_pbds; #define oset tree<ll, null_type,less<ll>, rb_tree_tag,tree_order_statistics_node_update> // use pair for ms // my io library :D #define m1(x) template<class T, class... U> void x(T&& a, U&&... b) #define m2(x) (ll[]){(x forward<U>(b),0)...} m1(pr){cout << forward<T>(a); m2(cout << " " <<); cout << "\n";} m1(re){cin >> forward<T>(a); m2(cin >>);} const ll cap = 5e4+1; ll dist[cap], k; vector<pair<ll,ll>> adj[cap]; vector<tuple<ll,ll,ll>> adj_by_layer[cap]; /* void dijkstra(ll s){ priority_queue<pair<ll,ll>> pq; fill(dist, dist+cap, 1e18); pq.push({0, s}); dist[s] = 0; while (!pq.empty()){ pair<ll,ll> oknext = pq.top(); pq.pop(); oknext.first *= -1; for (auto u: adj[oknext.second]){ if (dist[oknext.second] + u.second < dist[u.first]){ dist[u.first] = dist[oknext.second] + u.second; pq.push({-dist[u.first], u.first}); } } } } */ ll layer(ll a){ return a/k; } int main() { ios::sync_with_stdio(0); cin.tie(0); ll n, m, o; re(k, n, m, o); for (ll i{}; i < m; i++){ ll a, b, t; re(a, b, t); adj[a].eb(make_pair(b, t)); adj_by_layer[layer(a)].eb(make_tuple(a,b,t)); } ll nolayers = (n+k-1)/k; ll lastsz = n - k*(nolayers-1), log = ceil(log2(nolayers)); vector<vector<vector<vector<ll>>>> up(nolayers, vector<vector<vector<ll>>>(32, vector<vector<ll>>(k, vector<ll>(k, 1e18)))); for (ll i{}; i < nolayers; i++) { for (auto tup :adj_by_layer[i]) { ll a, b, t; tie(a, b, t) = tup; ll x = a % k, y = b % k; up[i][0][x][y] = min(up[i][0][x][y], t); } } for (ll i{}; i < nolayers; i++){ for (ll j = 1; j < log; j++){ if (i + (1LL<<j) >= nolayers) continue; ll xlim = (i == nolayers - 1 ? lastsz : k); ll ylim = (i + ((1LL<<j)) == nolayers - 1 ? lastsz : k); ll nexlim = ((i + (1LL<<(j-1)) == nolayers-1) ? lastsz : k); for (ll x{}; x < xlim; x++){ for (ll y{}; y < ylim; y++){ for (ll mid{}; mid < nexlim; mid++){ up[i][j][x][y] = min(up[i][j][x][y], up[i][j-1][x][mid] + up[(1<<(j-1))+i][j-1][mid][y]); } } } } } for (ll i{}; i < o; i++){ ll a, b; re(a, b); ll la = layer(a), lb = layer(b); ll diff = lb - la, curl = la; vector<ll> cur(k, 1e18); cur[a%k] = 0; ll ans = 0; for (ll j{}; j < log; j++){ if (diff & ((1LL<<j))){ ll curlsz = (curl == nolayers-1 ? lastsz : k); ll nexsz = (curl + ((1LL<<j)) == nolayers-1 ? lastsz : k); vector<ll> nex(nexsz, 1e18); for (ll x{}; x < curlsz; x++){ for (ll y{}; y < nexsz; y++){ nex[y] = min(nex[y], cur[x] + up[curl][j][x][y]); } } cur = nex; curl += ((1LL<<j)); } } ans = cur[b%k]; if (ans == (ll)1e18) pr(-1); else pr(ans); } }