use proconio::input_interactive;

fn main() {
    input_interactive! {
        alpha: char,
    }
    
    let mut pre = alpha;
    
    loop {
        println!("? {}{}", pre, alpha);
        
        input_interactive! {
            (cmd, s): (char, String),
        }
        
        match cmd {
        	'!' => { break; },
        	'?' => { pre = s.chars().last().unwrap(); },
        	_ => {},
        }
    }
}