#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cmath>
#include <tuple>
#include <bitset>

#define rep(i,n) for(i=0; i<n; ++i)
#define in(a) cin >> a
#define out(a,b) cout << a << b
using namespace std;
using lint = long long;

int main(void){
    lint i, j;
    lint p, n, m;
    int left=1, right=pow(10,9);
    while(true){
        cout << "? " << left+(right-left+1)/2 << endl;
        int input;
        cin >> input;
        if(input==1){
            left=left+(right-left+1)/2;
        }
        else{
            right=left+(right-left+1)/2-1;
        }
        if(left==right) break;
    }
    cout << "! " << left << endl;
    return 0;
}