#include <bits/stdc++.h>
using namespace std;

#undef _P
#define _P(...) (void)printf(__VA_ARGS__)
#define FORR(x,arr) for(auto&& x:arr)
#define FOR(i,a,b) for (int i = (a); i < (b); i++)
#define RFOR(i,a,b) for (int i = (b)-1; i >= (a); i--)
#define REP(i,n) for (int i = 0; i < (n); i++)
#define RREP(i,n) for (int i = (n)-1; i >= 0; i--)
#define ALL(x) (x).begin(), (x).end()
#define BIT(n) (1LL<<(n))
#define SZ(x) ((int)(x).size())
#define fst first
#define snd second
#define DUMP( x ) cerr << #x << " = " << ( x ) << endl
typedef long long ll;
// -------------------------------------

bool check(int x) {
  _P("? %d\n", x);
  fflush(stdout);
  string res;
  cin >> res;
  return res == "1";
}

void Main() {
  // 1 が true
  int ok = 0;  // check が絶対trueになる値
  int ng = 1000000001;  // check が絶対falseになる値

  while (abs(ok - ng) > 1) {
    int mid = (ok + ng) / 2;
    bool c = check(mid);
    if (c) ok = mid;
    else ng = mid;
  }
  _P("! %d\n", ok);
  fflush(stdout);
}
int main() { cin.tie(0); ios::sync_with_stdio(false); Main(); return 0; }