#include <bits/stdc++.h>
#define fi first
#define se second
#define TASK "simproads"
#define pb push_back
#define all(r) (r).begin(), (r).end()
#define ll long long
#define MASK(i) (1 << (i))
#define BIT(x, i) ((x) >> (i) & 1)
using namespace std;
const int LOG = 19;
const int oo = 1e9 + 7;
const ll loo = (ll)1e18 + 7;
const int N = 5e4 + 7;
int n, k, m, q, pre[N], dist[N];
vector<pair<int, int>> g[N], queries;
void dijkstra(int root){
for (int i = 1; i <= n; i++) dist[i] = oo;
dist[root] = 0;
priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> kew;
kew.push({0, root});
while (!kew.empty()){
auto k = kew.top();
kew.pop();
if (k.fi > dist[k.se]) continue;
for (auto u : g[k.se]){
if (u.se + k.fi < dist[u.fi]){
dist[u.fi] = u.se + k.fi;
kew.push({dist[u.fi], u.fi});
}
}
}
}
struct DSU{
vector<int> par, sz;
int n;
DSU(int _n){
n = _n;
par.resize(n + 7);
sz.resize(n + 7);
for (int i = 1; i <= n; i++) {
par[i] = i;
sz[i] = 1;
}
}
int find_node(int u){
if (u == par[u]) return u;
else return par[u] = find_node(par[u]);
}
bool unify(int u, int v){
u = find_node(u);
v = find_node(v);
if (u == v) return false;
if (sz[u] < sz[v]) swap(u, v);
sz[u] += sz[v];
par[v] = u;
return true;
}
bool same(int u, int v) {
if (find_node(u) == find_node(v)) return true;
return false;
}
};
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
// freopen(TASK".inp", "r", stdin);
// freopen(TASK".out", "w", stdout);
cin >> k >> n >> m >> q;
for (int i = 1; i <= m; i++){
int u, v, c; cin >> u >> v >> c;
u++; v++;
g[u].pb({v, c});
}
bool flag = true;
for (int i = 1; i <= q; i++){
int u, v; cin >> u >> v;
u++; v++;
if (u != 1) flag = false;
queries.pb({u, v});
}
if (k == 1){
for (int i = 1; i <= n; i++) {
pre[i] += pre[i - 1];
if (g[i].size()) pre[i + 1] += g[i][0].se;
}
DSU dsu(n);
for (int i = 1; i <= n; i++){
if (g[i].size()) dsu.unify(i, i + 1);
}
for (int i = 0; i < queries.size(); i++){
int u = queries[i].fi, v = queries[i].se;
if (!dsu.same(u, v)) cout << -1 << "\n";
else cout << pre[max(u, v)] - pre[min(u, v) - 1] << "\n";
}
}
else if (flag){
dijkstra(1);
for (auto u : queries){
if (dist[u.se] == oo) cout << -1 << "\n";
else cout << dist[u.se] << "\n";
}
}
else if (q <= 100){
for (auto u : queries){
dijkstra(u.fi);
if (dist[u.se] == oo) cout << -1 << "\n";
else cout << dist[u.se] <<"\n";
}
}
return 0;
}
