#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

int main() {
    long long l = 1, r = 1000000000;
    long long ans;
    while ( true ) {
        cout << "? " << (l+r)/2 << endl;
        cout << flush;
        long long ret;
        cin >> ret;
        if ( ret ) {
            if ( l == (l+r)/2 ) { ans = l; break; }
            l = (l+r)/2;
        }
        else {
            if ( r == (l+r)/2 - 1 ) { ans = r; break; }
            r = (l+r)/2 - 1;
        }
    }
    cout << "! " << ans << endl;

    return 0;
}