#include <bits/stdc++.h>

using namespace std;
    
typedef long long ll;
const int  N = 5e4 + 12, MOD = (int)1e9 + 7;

int k, n, m, q, b;
vector<pair<int,int>> g[N], o;
vector<ll> di[N];
const int inf = 1e9 + 1;
vector<ll> tr(vector<ll> prev,int l, int r) {
    vector<ll> ret(k,inf);
    assert(l % k == 0);
    for(int i = l; i <= r; i++) {
        int f = i % k;
        for(auto [to,w]:g[i]) {
            ret[to % k] = min(ret[to % k],prev[f] + w);
        }
    }
    return ret;
}
void prec() {
    for(int i = (int)o.size() - 1; i >= 0; i--) {
        if(i % b == 0) {
            int nx = i + b;
            int l = o[i].first, r = o[i].second;
            for(int j = l; j <= r; j++) {
                vector<ll> dd(k,inf);
                dd[j%k] = 0;
                for(int _i = i + 1; _i < (int)o.size(); _i++) {
                    vector<ll> nv = tr(dd,o[_i - 1].first,o[_i - 1].second);
                    for(auto f:nv) {    
                        di[j].push_back(f);
                    }
                    dd = nv;
                }
            }
        }
    }
}
void test() {
    cin >> k >> n >> m >> q;
    for(int i = 1; i <= m; i++) {
        int a, b, c;
        cin >> a >> b >> c;
        g[a].push_back({b,c});
    }
    for(int i = 0; i <= n; i++) {
        int l = i * k, r = (i + 1) * k - 1;
        if(l >= n) break;
        if(r >= n) {
            r = n - 1;
        }
        o.push_back({l,r});
    }
    for(int i = 0; i < n; i++) {
        sort(g[i].begin(),g[i].end());
        vector<pair<int,int>> nv;
        for(auto [x,y]:g[i]) {
            if(nv.empty() || nv.back().first != x) {
                nv.emplace_back(x,y);
            }
        }
        g[i].swap(nv);
        assert((int)g[i].size() <= k);
    }
    b = 300;
    // b = 1;
    prec();
    // return;
    while(q--) {
        int a, b;
        cin >> a >> b;
        if(a / k >= b / k) {
            cout << -1 << '\n';
            continue;
        }
        int x = a / k, y = b / k;
        vector<ll> cur(k,inf);
        cur[a%k] = 0;
        while(x % b != 0) {
            x++;
            cur = tr(cur,o[x - 1].first,o[x - 1].second);
            if(x == y) {
                break;
            }
        }
        ll res = inf;
        if(x == y) {
            res = cur[y % k];
        } else {
            for(int i = 0; i < k; i++) {
                int nx = (x + 1) * k;
                res = min(res,di[o[x].first + i][b - nx] + cur[i]);
            }
        }
        if(res == inf) res = -1;
        cout << res << '\n';
    }
}
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int t = 1; 
    // cin >> t;
    while(t--) 
        test();

    return 0;
}