/*
Jackson Simoneau
SI@UCF 2026 - Intro to Competitive Programming

Solution to Hidden Integer: https://cses.fi/problemset/task/3112
*/

#include <bits/stdc++.h>
using namespace std;

int main() {
    //Binary search for the answer
    int lo = 1, hi = 1000000000;
    while(lo < hi) {
        int m = (lo + hi) / 2;
        //Ask if the midpoint is lower than x
        //Make sure to use endl to flush the output!
        cout << "? " << m << endl;

        //Read in the response from the judge
        string ans;
        cin >> ans;
        
        //If YES, x is at least m+1
        //Otherwise, x is at most m
        if(ans == "YES") {
            lo = m+1;
        } else {
            hi = m;
        }
    }

    //Output the value of x
    cout << "! " << lo << endl;
}