use proconio::input;
use std::io::{stdout, Write};
fn main() {
    let mut ng = 10_i32.pow(9) + 1;
    let ok = 0;
    for _ in 0..30 {
        let mid = (ng + ok) / 2;
        println!("{}", mid);
        stdout().flush().unwrap();
        input! { n: usize }
        if n == 0 {
            ng = mid;
        } else {
            return;
        }
    }
}