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

#define For(i, a, b) for(int i = (a); i < (b); i++)
#define rep(i, n) For(i, 0, n)
#define rFor(i, a, b) for(int i = (a); i >= (b); i--)
#define ALL(v) (v).begin(), (v).end()
#define rALL(v) (v).rbegin(), (v).rend()

using lint = long long;
using ld = long double;

int INF = 2000000000;
lint LINF = 1000000000000000000;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    auto ask = [](int x) -> int {
        cout << x << "\n";
        cout.flush();
        int r;
        cin >> r;
        return r;
    };
    int l = 0, r = 1000000010;
    while (r - l > 1) {
        int mid = (l + r) / 2;
        if (ask(mid)) {
            return 0;
        } else {
            r = mid;
        }
    }
}