#include <bits/stdc++.h>
using namespace std;
int main(){
  int T;
  cin >> T;
  for (int i = 0; i < T; i++){
    int N, A, W, K;
    cin >> N >> A >> W >> K;
    if (K != N || W == 0){
      if (A < K - 1){
        if (W >= N - K + 1){
          cout << -1 << endl;
        } else {
          cout << ":(" << endl;
        }
      } else if (A % K == K - 1){
        cout << A / K << endl;
      } else {
        cout << A / K - 1 << endl;
      }
    } else {
      long long sum = A - (long long) W * (W + 1) / 2;
      int r = (sum % N + N) % N;
      long long q = (sum - r) / N;
      if (r != N - 1){
        q--;
      }
      long long fv = 0, tv = W + 1;
      while (tv - fv > 1){
        long long mid = (tv + fv) / 2;
        if (- mid * (mid + 1) / 2 <= q){
          tv = mid;
        } else {
          fv = mid;
        }
      }
      long long s = - tv * (tv + 1) / 2;
      if (s + A > q){
        cout << q << endl;
      } else {
        cout << s + A << endl;
      }
    }
  }
}