#include <bits/stdc++.h>
#define rep(i,n) for (int i=0; i < (n); i++)
using namespace std;
using ll = long long;

int main(){
    ios::sync_with_stdio(false);
    int safe = 0, out=1000;
    int t=25;

    while(t--){
        int c = (safe+out)/2;
        cout << "?" << c << endl;
        string s; cin >> s;
        if(s=="safe"){
            safe = c;
        }else if(s=="out"){
            if(t==0) break;
            t--;
            cout << "?" << c+1 << endl;
            cin >> s;
            if(s=="out"){
                out = c;
            }else{
                safe = c+1;
            }
        }
    }
    cout << safe << endl;
}