#include "bits/stdc++.h"
#define REP(i,n,N) for(ll i=(n); i<(N); i++)
#define RREP(i,n,N) for(ll i=(N-1); i>=n; i--)
#define CK(n,a,b) ((a)<=(n)&&(n)<(b))
#define ALL(v) (v).begin(),(v).end()
#define p(s) cout<<(s)<<endl
#define p2(a,b) cout<<(a)<<" "<<(b)<<endl
typedef long long ll;
using namespace std;
const ll inf=1e18;


int main(){
    int l=1, r=1e9;
    int x;
    while(r-l>1){
        int mid=(r+l)/2;
        cout<<"? "<<mid<<endl;
        cin>>x;
        if(x) l=mid;
        else r=mid;
    }
    cout<<"! "<<l<<endl;
}