#line 1 "main.cpp"
#include <bits/stdc++.h>

using namespace std;

void solve() {
  using Re = double;
  auto ask = [&](Re y) -> bool {
    cout << "? " << y << endl;
    cout.flush();
    string S;
    cin >> S;
    return S == "Yes";
  };

  auto ans = [&](Re x) -> void {
    cout << "! " << x << endl;
    cout.flush();
  };

  Re lo = 1e-6, hi = 12.22e74;
  for (int i = 0; i < 24; ++i) {
    Re mi = sqrt(lo * hi);
    if (ask(mi)) {
      lo = mi;
    } else {
      hi = mi;
    }
  }
  ans(sqrt(lo * hi));
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(15);

  int t;
  cin >> t;
  for (int i = 0; i < t; i++) {
    // input();
    solve();
  }
}