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

// 可変引数repマクロ https://trap.jp/post/1224/
#define rep1(a) for (long long i = 0; i < (long long)a; i++)
#define rep2(i, a) for (long long i = 0; i < (long long)a; i++)
#define rep3(i, a, b) for (long long i = (long long)a; i <= (long long)b; i++)
#define rep4(i, a, b, c) for (long long i = (long long)a; i <= (long long)b; i += (long long)c)
#define overload4(a, b, c, d, e, ...) e
#define rep(...) overload4(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)

#define printYesNo(is_ok) puts(is_ok ? "Possible" : "Impossible")
#define ALL(v) v.begin(), v.end()
#define RALL(v) v.rbegin(), v.rend()
#define SORT(v) sort(ALL(v))
#define RSORT(v) sort(RALL(v))
#define REVERSE(v) reverse(ALL(v))

template <class T>
using pq_asc = priority_queue<T, vector<T>, greater<T>>;
template <class T>
using pq_des = priority_queue<T>;

template <typename T>
void printlnVector(T v)
{
  for (auto n : v)
  {
    cout << n << endl;
  }
}

template <typename T>
void printVector(T v)
{
  for (auto n : v)
  {
    cout << n << " ";
  }
  cout << endl;
}

template <typename T>
enable_if_t<is_integral_v<T>, T>
bin_search(T ok, T ng, function<bool(T)> check)
{
  while (max(ok, ng) - min(ok, ng) > 1)
  {
    T mid = midpoint(ok, ng);
    (check(mid) ? ok : ng) = mid;
  }
  return ok;
}

int main()
{

  auto check = [](long long x) -> bool
  {
    cout << x << endl;
    bool r;
    cin >> r;

    if (r)
    {
      exit(0);
    }

    return r;
  };

  long long ans = bin_search<long long>(0, 1000000000, check);
  // cout << ans << endl;

  return 0;
}