#include <bits/stdc++.h>
using namespace std;
const int INF = INT_MAX;
const long long LINF = LLONG_MAX;
const unsigned long long ULINF = ULLONG_MAX;
const double EPS = 0.000001;
long long solve1(long long a, long long b, long long l, long long t,
                 long long m) {
  double ans = (1. * (4 * a * a - 12 * a * b + 9 * b * b + 8 * a * b * l -
                      12 * b * b * l + 4 * b * b * l * l + 8 * b * m * t)) /
               (b * b);
  ans = pow(ans, 0.5);
  ans = (1. * (ans * b + b - 2 * a)) / (2 * b);
  return floor(ans);
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  long long a, b, n;
  cin >> a >> b >> n;
  while (n--) {
    long long l, t, m;
    cin >> l >> t >> m;
    double right_solution =
        (1. * (-a * a + 3 * a * b - 2 * b * b - 2 * a * b * l + 3 * b * b * l -
               b * b * l * l + b * t + t * t)) /
        (2 * b * t);
    long long ans;
    if (m < right_solution)
      ans = solve1(a, b, l, t, m);
    else
      ans = floor((1. * (-a + b + t)) / b);
    if (ans < l) ans = -1;
    cout << ans << "\n";
  }
  return 0;
}
