#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <cmath>
#include <iostream>
#include <queue>
#include <list>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;

int main(){
  int lb = 0, ub = 1000000001;
  while(ub-lb>1){
    int res;
    int mid = (lb+ub)/2;
    printf("? %d\n", mid);
    fflush(stdout);
    scanf("%d", &res);
    fflush(stdin);
    if(res==0) lb = mid;
    else ub = mid;
  }

  printf("! %d\n", ub);
  fflush(stdout);
  
  return 0;
}