#include <cstring>
#include <algorithm>
#include <cstdio>
#include <iostream>
#define REP(i,a,b) for(i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
/* ここからが本編 */
/* */
/* 入力開始！ */
/* 入力終了！ */
/* ll_pow(x,n)はx^nを返すよ！ */
ll ll_pow(ll x,ll n) {
   ll res = 1;
   while(n > 0) {
      if(n&1) res = res * x;
      x = x * x;
      n >>= 1;
   }
   return res;
}
int main(void)
{
  int i,j,k;
  ll left = 0, right = ll_pow(10,9)+1,mid;
  while(left < right) {
    mid = (left+right)/2;
    int rep;
	cout << "? " << mid << endl; 
    cin >> rep;
    if(rep) left = mid;
    else right = mid-1;
	if(mid == (left+right)/2) break;
  }
  cout << "! " << mid << endl;
  return 0;
}