/**
* Author: Anil Byar
**/
#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
// using namespace __gnu_pbds;
using namespace std;
// template<class T>
// using ordered_set = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)(x).size()
#define ft first
#define sd second
#define pb push_back
// Source: https://codeforces.com/blog/entry/68809
// { start
void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '"' << x << '"';}
void __print(const string &x) {cerr << '"' << x << '"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifndef ONLINE_JUDGE
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif
// } end
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<pii> vii;
typedef vector<ll> vl;
typedef vector<pll> vll;
typedef vector<vi> vvi;
typedef vector<vii> vvii;
typedef vector<vl> vvl;
#define dbg if(0)
const ll MOD = 1e9+7;
const ll INFLL = 1e18+5;
const int INF = 1e9;
// const int maxK = 18;
void printbit(int x, int len) {string s="\n";while(len--){s=((x%2)?'1':'0')+s;x/=2;} cout<<s;}
template<class T>
istream& operator>>(istream&in, vector<T>&v){
for (T& x:v) in>>x;
return in;
}
template<class T>
ostream& operator<<(ostream&out, vector<T>&v){
for (T& x:v) out<<x<<' ';
cout<<'\n';
return out;
}
void solve(){
int k, n, m, o;
cin>>k>>n>>m>>o;
const int maxN = (n+1)/k + 5;
const int maxK = log2(maxN) + 1;
ll dp[maxN][k][k][maxK];
memset(dp, 63, sizeof(dp));
for (int i = 0;i<m;i++){
int u, v, w;
cin>>u>>v>>w;
dp[u/k][u%k][v%k][0] = w;
}
for (int j = 1;j<=maxK;j++){
for (int i = 0;i<(n+k-1)/k;i++){
for (int r1 = 0;r1<k;r1++){
for (int r2 = 0;r2<k;r2++){
for (int m = 0;m<k;m++){
if (i+(1<<(j-1))>=maxN) continue;
dp[i][r1][r2][j] = min(dp[i][r1][r2][j], dp[i][r1][m][j-1] + dp[i+(1<<(j-1))][m][r2][j-1]);
}
}
}
}
}
while(o--){
int a, b;cin>>a>>b;
int from = a/k;
int fr = a%k;
int to = b/k;
int tr = b%k;
// int ans = INFLL;
int up = to - from;
ll ans[k]{};
memset(ans, 63, sizeof(ans));
ans[fr] = 0;
for (int i = 0;i<maxK;i++){
if (up>>i&1){
ll tmp[k]{};
memset(tmp, 63, sizeof(tmp));
for (int ii = 0;ii<k;ii++){
for (int j = 0;j<k;j++){
tmp[ii] = min(tmp[ii], ans[j]+dp[from][j][ii][i]);
}
}
for (int ii = 0;ii<k;ii++) ans[ii] = tmp[ii];
from += (1<<i);
}
}
if (ans[tr]==4557430888798830399ll) ans[tr] = -1;
cout<<ans[tr]<<'\n';
}
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
// #define _DEBUG
#ifdef _DEBUG
freopen("input.txt", "r", stdin);
freopen("output.out", "w", stdout);
int tt = clock();
#endif
int t=1, i = 1;
// cin>>t;
while(t--){
// cout<<"Case #"<<i++<<": ";
solve();
cout<<'\n';
}
#ifdef _DEBUG
cerr << "TIME = " << (float)(clock() - tt)/CLOCKS_PER_SEC << endl;
tt = clock();
#endif
}
