using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static long[] NList => ReadLine().Split().Select(long.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var ok = 0;
        var ng = 1003;
        while (ng - ok > 1)
        {
            var mid = (ok + ng) / 2;
            if (IsSafe(mid)) ok = mid;
            else
            {
                if (IsSafe(mid + 1)) ok = mid;
                else ng = mid;
            }
        }
        WriteLine("! " + ok);
    }
    static Dictionary<int, bool> dic = new Dictionary<int, bool>();
    static bool IsSafe(int n)
    {
        if (dic.ContainsKey(n)) return dic[n];
        WriteLine($"? {n}");
        var res = ReadLine() == "safe";
        dic[n] = res;
        return res;
    }
}