#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> PP;
// #define MOD 1000000007
#define MOD 998244353
#define INF 2305843009213693951
#define PI 3.141592653589
#define setdouble setprecision
#define REP(i,n) for(ll i=0;i<(n);++i)
#define OREP(i,n) for(ll i=1;i<=(n);++i)
#define RREP(i,n) for(ll i=(n)-1;i>=0;--i)
#define ORREP(i,n) for(ll i=(n);i>=1;--i)
#define rep(i,a,b) for(ll i=(a);i<=(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define chmin(k,m) k = min(k,m)
#define chmax(k,m) k = max(k,m)
#define GOODBYE do { cout << "-1" << endl; return 0; } while (false)
#define MM <<" "<<
#define Endl endl

ll ask(ll x){
  cout << x << endl;
  ll r;
  cin >> r;
  if(r==-1){
    exit(1);
  }
  return r;
}

int main(void){
    //cin.tie(nullptr);
    //ios::sync_with_stdio(false);
    
    ll M = 30;
    ll ok = 0, ng = 1'000'000'001;
    
    while(abs(ok-ng)>1){
      ll mid = (ok+ng)/2;
      ll r = ask(mid);
      
      if(r==1){
        return 0;
      }
      ng = mid;
    }

    return 0;
    
}