#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#ifdef DEBUG
#include <time.h>
#endif
#define all(a) (a).begin(), (a).end()
#define rev(a) (a).rbegin(), (a).rend()
#define F first
#define S second
int recur_depth = 0;
#ifdef DEBUG
#define dbg(x) \
{ \
++recur_depth; \
auto x_ = x; \
--recur_depth; \
cerr << string(recur_depth, '\t') << "\e[91m" << __func__ << ":" \
<< __LINE__ << "\t" << #x << " = " << x_ << "\e[39m" << endl; \
}
#else
#define dbg(x)
#endif
using namespace std;
using namespace __gnu_pbds;
typedef pair<int, int> ii;
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> llll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<pair<int, int>> vii;
typedef vector<vii> vvii;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<pair<ll, ll>> vll;
typedef vector<vll> vvll;
typedef vector<bool> vb;
template <class type1>
using ordered_set = tree<type1, null_type, less<type1>, rb_tree_tag,
tree_order_statistics_node_update>;
template <typename A, typename B>
ostream &operator<<(ostream &os, const pair<A, B> &p) {
return os << '(' << p.first << ", " << p.second << ')';
}
template <typename T_container, typename T = typename enable_if<
!is_same<T_container, string>::value,
typename T_container::value_type>::type>
ostream &operator<<(ostream &os, const T_container &v) {
os << '{';
string sep;
for (const T &x : v)
os << sep << x, sep = ", ";
return os << '}';
}
const ll MOD = 1e9 + 7;
// const ll MOD = 998244353;
const ll INF = 1e18;
const ld EPS = 1e-9;
const int MAX_N = 5e4 + 10;
const int MAX_K = 6;
int k, n, m, o;
ll dist[MAX_N][MAX_K];
int block[MAX_N], mod[MAX_N];
ll dp[MAX_N];
void solve() {
cin >> k >> n >> m >> o;
for (int i = 0; i <= n; i++)
for (int j = 0; j <= k; j++)
dist[i][j] = INF;
for (int i = 0; i < m; i++) {
int u, v;
ll t;
cin >> u >> v >> t;
dist[u][v % k] = t;
}
for (int i = 0; i <= n; i++)
block[i] = i / k, mod[i] = i % k;
while (o--) {
int a, b;
cin >> a >> b;
if (block[a] >= block[b]) {
cout << "-1\n";
continue;
}
for (int i = 0; i <= n; i++)
dp[i] = INF;
dp[b] = 0;
int idx = b - mod[b];
int final_idx = a - mod[a];
for (idx -= k; idx >= final_idx; idx -= k) {
for (int i = idx; i < idx + k; i++) {
for (int j = 0; j < k; j++)
dp[i] =
min(dp[i], (idx + k + j <= n ? dp[idx + k + j] : 0) + dist[i][j]);
}
}
if (dp[a] >= INF)
cout << "-1\n";
else
cout << dp[a] << '\n';
}
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(NULL);
clock_t start = clock();
int test_cases = 1;
// cin >> test_cases;
while (test_cases--)
solve();
#ifdef DEBUG
cerr << fixed << setprecision(10)
<< "\nTime Taken: " << (double)(clock() - start) / CLOCKS_PER_SEC
<< "s\n";
#endif
return 0;
}
