#include <bits/stdc++.h>

namespace solver{
  bool query(int x){
    std::cout << "? " << x << "\n";
    std::string ret; std::cin >> ret;
    if(ret == "safe") return true;
    else return false;
  }

  void answer(int x){
    std::cout << "! " << x << "\n";
  }
  
  void solve(){
    int N, D = 0;

    int lb = 0, ub = 1001;
    while(abs(lb - ub) > 1){
      int mid = (lb + ub) / 2;

      if(query(mid)){
        lb = mid;
      }else{
        if(query(mid + 1)){
          lb = mid;
          D = std::gcd(D, mid);
        }else{
          ub = mid;
        }
      }
    }

    N = ub;

    std::cerr << N << " " << D << "\n";

    int ans = 0;
    for(int i = 0; i < N; ++i){
      if(D == 0 or i % D != 0){
        ans = std::max(ans, i);
      }
    }

    answer(ans);
  }
}

int main(){
  solver::solve();
  return 0;
}