#include <bits/stdc++.h>
#include <cassert>
using namespace std;
using ll = long long int;
using u64 = unsigned long long;
using pll = pair<ll, ll>;
// #include <atcoder/all>
// using namespace atcoder;
#define REP(i, a, b) for (ll i = (a); i < (b); i++)
#define REPrev(i, a, b) for (ll i = (a); i >= (b); i--)
#define ALL(coll) (coll).begin(), (coll).end()
#define SIZE(v) ((ll)((v).size()))
#define REPOUT(i, a, b, exp, sep) REP(i, (a), (b)) cout << (exp) << (i + 1 == (b) ? "" : (sep)); cout << "\n"

// @@ !! LIM(f:intDiv)

// ---- inserted function f:intDiv from util.cc
// imod, divFloor, divCeil

// imod(x, y) : remainder of x for y
// for y > 0:
//   imod(x, y)  = r where x = dy + r, 0 <= r < y
//   imod(x, -y) = r where x = dy + r, 0 >= r > y
// Thus, imod( 10,  7) =  3
//       imod(-10,  7) =  4
//       imod( 10, -7) = -4
//       imod(-10, -7) = -3
ll imod(ll x, ll y) {
  ll v = x % y;
  if ((x >= 0) == (y >= 0)) return v;
  else                      return v == 0 ? 0 : v + y;
}

// Integer Division; regardless pos/neg
ll divFloor(ll x, ll y) {
  if (x > 0) {
    if (y > 0) return x / y;
    else       return (x - y - 1) / y;
  }else {
    if (y > 0) return (x - y + 1) / y;
    else       return x / y;
  }
}

ll divCeil(ll x, ll y) {
  if (x > 0) {
    if (y > 0) return (x + y - 1) / y;
    else       return x / y;
  }else {
    if (y > 0) return x / y;
    else       return (x + y + 1) / y;
  }
}
//   Just a note.  For d \in Z and t \in R,
//       d < t <=> d < ceil(t),     d <= t <=> d <= floor(t),
//       d > t <=> d > floor(t),    d >= t <=> d >= ceil(t).

// ---- end f:intDiv

// @@ !! LIM -- end mark --

int main(/* int argc, char *argv[] */) {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << setprecision(20);

  auto ask = [&](ll x) -> ll {
    cout << "? " << x << endl;
    ll t; cin >> t;
    return t;
  };
  auto answer = [&](ll x) -> void {
    cout << "! " << x << endl;
  };

#if DEBUG
  ll lim = 10;
#else
  ll lim = 1e6;
#endif
  ll lo = 1, hi = lim;
  ll prev = 1;
  ll cur = lim;
  cout << 1 << endl;
  while (lo < hi) {
    ll t = ask(cur);
    if (t) {
      if (prev < cur) {
        lo = divCeil(lo + hi, 2);
        prev = cur;
        cur = lo - (prev - hi);
      }else {
        hi = divFloor(lo + hi, 2);
        prev = cur;
        cur = hi + (lo - prev);
      }
    }else {
      if (prev < cur) {
        hi = divFloor(lo + hi, 2);
        prev = cur;
        cur = lo - (prev - hi);
      }else {
        lo = divCeil(lo + hi, 2);
        prev = cur;
        cur = hi + (lo - prev);
      }
    }
  }
  answer(hi);

  return 0;
}