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

#ifdef LOCAL
#include <debug.hpp>
#else
#define debug(...)
#endif

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(20);

    auto check = [&](int x) -> bool {
        cout << x << endl;
        int r;
        cin >> r;
        if (r == -1) exit(0);
        return r == 1;
    };

    constexpr int M = 30;
    int ok = 0, ng = 1e9 + 1;
    for (int iter = 0; iter < M - 1; iter++) {
        int mid = midpoint(ok, ng);
        (check(mid) ? ok : ng) = mid;
    }

    check(ok);
}