#include<bits/stdc++.h>
using namespace std;
const int maxN = 1e5;
const int lg = 17;
const int inf_set = 0x3f;
const int inf_comp = 0x3f3f3f3f;
int k;
vector<pair<int,int>> graph[maxN];
//pair<int,int> par[maxN][lg];
int dp[maxN][5][lg][5];
bool vis[maxN];
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int t, n, m, a, b, c, d;
cin >> k >> n >> m >> t;
queue<int> tv;
//memset(graph, 0, sizeof(graph));
//memset(par, -1, sizeof(par));
memset(dp, inf_set, sizeof(dp));
memset(vis, 0, sizeof(vis));
// EDGES
for(int i = 0; i < m; ++i){
cin >> a >> b >> d;
graph[a].push_back({b,d});
dp[a/k][a%k][0][b%k] = d;
}
// EXPLORING THE GRAPH
for(int deepness = 0; deepness < (n+k-1)/k; ++deepness){
for(int mod = 0; mod < k; ++mod){
for(int i = 1; i < lg; ++i){ // Layers to go up
for(int j = 0; j < k; ++j){ // Mod of the layer you go up to
for(int h = 0; h < k; ++h){ // Mod of the layer you transverse
if(deepness + (1<<(i-1)) < (n+k-1)/k) dp[deepness][mod][i][j] = min(dp[deepness][mod][i][j], dp[deepness][mod][i-1][h] + dp[deepness + (1<<(i-1))][h][i-1][j]);
//cout << deepness << ' ' << mod << ' ' << i << ' ' << j << ' ' << h << '\n';
}
}
}
}
}
// QUERIES
int queries[k][k]; // New layer, Mod
int temp[k][k];
while(t--){
cin >> a >> b;
if((b/k) <= (a/k)) cout << -1 << '\n';
else{
memset(queries, inf_set, sizeof(queries));
for(int i = 0; i < k; ++i) queries[i][i] = 0;
c = a/k;
d = (b/k) - (a/k); // distance from one to another
for(int i = lg-1; i >= 0; --i){
if(d&(1<<i)){
//cout << i << '\n';
memset(temp, inf_set, sizeof(temp));
for(int ori = 0; ori < k; ++ori){
for(int dest = 0; dest < k; ++dest){
for(int mid = 0; mid < k; ++mid){
temp[ori][dest] = min(temp[ori][dest], queries[ori][mid] + dp[c][mid][i][dest]);
}
}
}
memcpy(queries, temp, sizeof(temp));
c += (1<<i);
//if(c >= d) break;
}
}
if(queries[a%k][b%k] != inf_comp) cout << queries[a%k][b%k] << '\n';
else cout << -1 << '\n';
}
}
return 0;
}
