import java.util.*;

@SuppressWarnings("unused")
public class Main {

  private static void solve() {
    int t = ni();
    for (int i = 0; i < t; i++) {
      
      double leftEx = -20;
      double rightEx = Math.log(12.23e74);
      for (int j = 0; j < 5; j++) {
        double mid = (leftEx + rightEx) / 2;
        if (ask(Math.exp(mid))) {
          leftEx = mid;
        } else {
          rightEx = mid;
        }
      }

      double left = Math.exp(leftEx);
      double right = Math.exp(rightEx);
      for (int j = 0; j < 19; j++) {
        double mid = Math.sqrt(left * right);
        if (ask(mid)) {
          left = mid;
        } else {
          right = mid;
        }
      }

      answer((left + right) / 2);
    }
  }

  static double ans = -1;//3.1415926536;

  private static void answer(double y) {
    out.println(String.format("! %.12f", Math.min(12.22e74, y)));
    out.flush();
  }

  private static boolean ask(double x) {
    out.printf("? %.12f\n", Math.min(12.22e74, x));
    out.flush();

    if (ans >= 0) {
      return x <= ans;
    } else {
      var ret = next();
      if (ret.equals("Yes")) {
        return true;
      } else if (ret.equals("No")) {
        return false;
      } else {
        throw new RuntimeException("???");
      }
    }
  }

  private static long[] dijkstra(int[] a, int m) {
    final long[] d = new long[m];
    Arrays.fill(d, Long.MAX_VALUE / 2);
    d[0] = 0;
    PriorityQueue<long[]> q = new PriorityQueue<>((o1, o2) -> Long.compare(d[(int) o1[0]], d[(int) o2[0]]));

    int n = a.length;
    q.add(new long[] { 0, 0 });
    while (!q.isEmpty()) {
      var p = q.poll();
      int v = (int) p[0];
      var dv = p[1];
      if (dv > d[v])
        continue;

      for (int i = 0; i < n; i++) {
        int nv = (a[i] + v) % m;
        var nd = dv + a[i];
        if (nd < d[nv]) {
          d[nv] = nd;
          q.add(new long[] { nv, nd });
        }
      }
    }
    return Arrays.stream(d).map(v -> v >= Long.MAX_VALUE / 2 ? -1 : v).toArray();
  }

  public static void main(String[] args) {
    new Thread(null, new Runnable() {
      @Override
      public void run() {
        long start = System.currentTimeMillis();
        String debug = args.length > 0 ? args[0] : null;
        if (debug != null) {
          try {
            is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug));
          } catch (Exception e) {
            throw new RuntimeException(e);
          }
        }
        reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768);
        solve();
        out.flush();
        tr((System.currentTimeMillis() - start) + "ms");
      }
    }, "", 64000000).start();
  }

  private static java.io.InputStream is = System.in;
  private static java.io.PrintWriter out = new java.io.PrintWriter(System.out);
  private static java.util.StringTokenizer tokenizer = null;
  private static java.io.BufferedReader reader;

  public static String next() {
    while (tokenizer == null || !tokenizer.hasMoreTokens()) {
      try {
        tokenizer = new java.util.StringTokenizer(reader.readLine());
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
    return tokenizer.nextToken();
  }

  private static double nd() {
    return Double.parseDouble(next());
  }

  private static long nl() {
    return Long.parseLong(next());
  }

  private static int[] na(int n) {
    int[] a = new int[n];
    for (int i = 0; i < n; i++)
      a[i] = ni();
    return a;
  }

  private static char[] ns() {
    return next().toCharArray();
  }

  private static long[] nal(int n) {
    long[] a = new long[n];
    for (int i = 0; i < n; i++)
      a[i] = nl();
    return a;
  }

  private static int[][] ntable(int n, int m) {
    int[][] table = new int[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[i][j] = ni();
      }
    }
    return table;
  }

  private static int[][] nlist(int n, int m) {
    int[][] table = new int[m][n];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[j][i] = ni();
      }
    }
    return table;
  }

  private static int ni() {
    return Integer.parseInt(next());
  }

  private static void tr(Object... o) {
    if (is != System.in)
      System.out.println(java.util.Arrays.deepToString(o));
  }
}