#![allow(unused_imports)]
#![allow(unused_must_use)]

//use rand::Rng;
use std::io::stdin;

enum State {
    Locked,
    Failed,
    Unlocked
}

fn main() {


    let code = String::from("1234");
    let mut state= State::Locked;
    let mut entry = String::new();


    loop {
        match state {
            State::Locked=>{
                let mut input = String::new();
                match stdin().read_line(&mut input) {
                    Ok(_)=>{
                        entry.push_str(&input.trim_end())
                    }
                    Err(_)=> continue
                }
                if entry==code {
                    state= State::Unlocked;
                    continue;
                }
                if !code.starts_with(&entry){
                    state=State::Failed;
                }
            }
            State::Failed=>{
                println!("FAILED");
                entry.clear(); //""
                state= State::Locked;
                continue;
            }
            State::Unlocked=>{
                println!("UNLOCKED");
                return;
            }
        }
    }
}