#include<bits/stdc++.h>
using namespace std;
void DBG() { cerr << "]\n"; }
template<class H, class... T> void DBG(H h, T... t) {
cerr << h; if(sizeof...(t)) cerr << ", ";
DBG(t...);
}
#ifdef LOCAL
#define dbg(...) cerr << "[" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__)
#else
#define dbg(...) 0
#endif // LOCAL
#define FOR(i,a,b) for(int i = (a) ; i<(b) ; i++)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for(int i = (b)-1 ; i>=(a) ; i--)
#define R0F(i,a) ROF(i,0,a)
#define each(e,a) for(auto &e : (a))
#define sz(v) (int)(v).size()
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
#define pb push_back
#define tcT template<class T
#define nl "\n"
using ll = long long;
using vi = vector<int>;
using pi = pair<int,int>;
using str = string;
tcT> using V = vector<T>;
tcT> using pqg = priority_queue<T,vector<T>,greater<T>>;
void setIO(string NAME = "") {
cin.tie(0)->sync_with_stdio(0);
if(sz(NAME)) {
freopen((NAME + ".inp").c_str(),"r",stdin);
freopen((NAME + ".out").c_str(),"w",stdout);
}
}
const int MOD = 1e9 + 7;
tcT> bool ckmin(T&a, const T&b) {
return b < a ? a = b, 1 : 0;
}
constexpr int p2(int x) { return 1<<x;}
const int MX = 50000, LG = 17;
int K, N, M, O;
int dp[MX][LG][5][5];
int ans[5][5], tmp[5][5];
void comb(int mn[5][5], int a[5][5], int b[5][5]) {
F0R(x,K) F0R(y,K) F0R(z,K) ckmin(mn[x][y], a[x][z] + b[z][y]);
}
void solve() {
cin>>K>>N>>M>>O;
memset(dp, 0x3f, sizeof dp);
F0R(i,M) {
int a, b, t;
cin>>a>>b>>t;
dp[a/K][0][a%K][b%K] = t;
}
FOR(j,1,LG) for(int i = 0; i+p2(j)<(N+K-1)/K; i++) comb(dp[i][j], dp[i][j-1], dp[i+p2(j-1)][j-1]);
while(O-->0) {
int a, b;
cin>>a>>b;
memset(ans, 0x3f, sizeof ans);
F0R(i,5) ans[i][i] = 0;
int cur = a/K, dst = b/K;
R0F(i,LG) if(cur + p2(i) <= dst) {
memset(tmp, 0x3f, sizeof tmp);
comb(tmp, ans, dp[cur][i]);
memcpy(ans, tmp, sizeof ans);
cur += p2(i);
}
cout << (ans[a%K][b%K] < MOD ? ans[a%K][b%K] : -1) << nl;
}
}
int main() {
setIO();
int t=1;
//cin>>t;
while(t-->0) {
solve();
}
return 0;
}
