fn main(){
    let mut sc = Scanner::new();
    let mut left = 0; // le
    let mut right = 1_000_000_010;
    while left + 1 < right {
        let mid = (left + right) / 2;
        println!("? {}", mid);
        use std::io::Write;
        std::io::stdout().flush().unwrap();

        if sc.next::<i32>() == 1 {
            left = mid;
        } else {
            right = mid;
        }
    }

    println!("! {}", left);
    use std::io::Write;
    std::io::stdout().flush().unwrap();
}

#[allow(dead_code)]
struct Scanner {
    buf: Vec<u8>, idx: usize, next: String,
}

#[allow(dead_code)]
impl Scanner {
    fn new() -> Scanner {
        Scanner { buf: vec![], idx: 0, next: String::new() }
    }

    fn next<T: std::str::FromStr>(&mut self) -> T {
        self.wrapped::<T>().unwrap()
    }

    fn vec<T: std::str::FromStr>(&mut self, n: usize) -> Vec<T> {
        let mut res = Vec::<T>::with_capacity(n);
        for _ in 0..n { res.push(self.next()) }
        res
    }

    fn wrapped<T: std::str::FromStr>(&mut self) -> Option<T> {
        if !self.read() {
            None
        } else {
            let res = self.next.parse::<T>().ok();
            self.next.clear();
            res
        }
    }

    fn read(&mut self) -> bool {
        if !self.next.is_empty() {
            true
        } else {
            self.next.clear();
            loop {
                match self.get_char() {
                    Some(c) if !c.is_whitespace() => {
                        self.next.push(c);
                        break;
                    },
                    Some(_) => continue,
                    None => return false,
                }
            }
            loop {
                match self.get_char() {
                    Some(c) if !c.is_whitespace() => self.next.push(c),
                    _ => return true,
                }
            }
        }
    }

    fn get_char(&mut self) -> Option<char> {
        if self.idx >= self.buf.len() {
            self.fill_buf();
            if self.idx >= self.buf.len() { return None }
        }
        self.idx += 1;
        Some(self.buf[self.idx - 1] as char)
    }

    fn fill_buf(&mut self){
        use std::io::BufRead;
        let reader = std::io::stdin();
        let mut buffer = reader.lock();
        let len = match buffer.fill_buf() {
            Ok(bytes) => {
                self.buf.resize(bytes.len(), b'\0');
                self.buf.copy_from_slice(bytes);
                bytes.len() as i32
            },
            Err(_) => -1,
        };
        self.idx = 0;
        if len >= 0 { buffer.consume(len as usize); }
    }
}