1183C.cpp

#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>

using namespace std;
using namespace __gnu_pbds;
typedef long long ll;

struct int_hash {
    static uint64_t splitmix64(uint64_t x) {
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};

struct pair_hash {
    size_t operator()(pair<int, int> x) const {
        return int_hash{}(x.first) ^ (int_hash{}(x.second) << 16);
    }
};

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const int MOD = 1000000007;
const ll INF = numeric_limits<ll>::max();
const int inf = 1e7;
const int MX = 100001; //check the limits, dummy

bool check(ll n, ll x, ll a, ll b, ll k) {
    return a*x + b*(n - x) < k;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    int q; cin >> q;
    while(q--) {
        ll k, n, a, b; cin >> k >> n >> a >> b;
        if(n * b >= k) cout << -1 << endl;
        else {
            ll lo = 0, hi = n + 1;
            while(hi - lo > 1) {
                ll mid = (hi - lo) / 2 + lo;
                if(check(n, mid, a, b, k)) lo = mid;
                else hi = mid; 
            }
            cout << lo << endl;
        }
    }
}