import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


enum LIM = 10L^^18;

long solve(const(long) N, const(long) A, const(long) W, const(long) K) {
  long ret = long.min;
  if (K == 1) {
    ret = A;
  } else if (K == N) {
    foreach (a; 0 .. 10) {
      if (W >= a) {
        const q = (W - a) / N, r = (W - a) % N;
        const me = q + ((0 < r) ? 1 : 0) + a;
        long lo = -LIM, hi = +LIM;
        for (; lo + 1 < hi; ) {
          const mid = (lo + hi) / 2;
          BigInt need;
          need += mid + (me * (me + 1) / 2);
          need += BigInt(max(r - 1, 0)) * (mid + 1 + ((q + 1) * (q + 2) / 2));
          need += BigInt(N - 1 - max(r - 1, 0)) * (mid + 1 + (q * (q + 1) / 2));
          ((need <= A) ? lo : hi) = mid;
        }
        if (lo > -LIM) {
          chmax(ret, lo);
        }
      }
    }
  } else {
    if (A >= K - 1) {
      ret = (A - (K - 1)) / K;
    } else if (W >= N - K) {
      ret = -1;
    } else {
      //
    }
  }
  return ret;
}

void main() {
  try {
    for (; ; ) {
      const numCases = readInt();
      foreach (caseId; 0 .. numCases) {
        const N = readLong();
        const A = readLong();
        const W = readLong();
        const K = readLong();
        const ans = solve(N, A, W, K);
        if (ans <= long.min) {
          writeln(":(");
        } else {
          writeln(ans);
        }
      }
    }
  } catch (EOFException e) {
  }
}