#include <algorithm>
#include <vector>
#include <cfloat>
#include <string>
#include <cmath>
#include <set>
#include <cstdlib>
#include <map>
#include <ctime>
#include <iomanip>
#include <functional>
#include <deque>
#include <iostream>
#include <cstring>
#include <queue>
#include <cstdio>
#include <stack>
#include <climits>
#include <sys/time.h>
#include <cctype>

using namespace std;

typedef long long ll;

int main() {
  int l = 0, r = 1000000000;
  for (int i = 0; i < 100; i++) {
    int p = (l+r)/2;
    printf("? %d\n", p);
    fflush(stdout);
    int y;
    scanf("%d", &y);
    if (y) {
      l = p;
    }else {
      r = p;
    }
  }
  printf("! %d\n", l);
  fflush(stdout);
}