Problem:
Score : 100 points

Problem Statement

The door of Snuke's laboratory is locked with a security code.

The security code is a 4-digit number. We say the security code is hard to enter when it contains two consecutive digits that are the same.

You are given the current security code S. If S is hard to enter, print Bad; otherwise, print Good.

Constraints

S is a 4-character string consisting of digits.

Input

Input is given from Standard Input in the following format:

S

Output

If S is hard to enter, print Bad; otherwise, print Good.

Sample Input 1

3776

Sample Output 1

Bad

The second and third digits are the same, so 3776 is hard to enter.

Sample Input 2

8080

Sample Output 2

Good

There are no two consecutive digits that are the same, so 8080 is not hard to enter.

Sample Input 3

1333

Sample Output 3

Bad

Sample Input 4

0024

Sample Output 4

Bad

Solution in Rust (1.15.1) (judge verdict: Accepted)

fn main() {
    let mut reader = acio::Reader::new();
    let s = reader.read::<String>();
    let mut prev = None;
    let mut bad = false;
    for c in s.chars() {
        if prev == Some(c) {
            bad = true;
        }
        prev = Some(c);
    }
    println!("{}", if bad { "Bad" } else { "Good" });
}

/// IO Module for AtCoder
#[allow(dead_code)]
mod acio {
    use std::fmt::Debug;
    use std::io::{stdin, Stdin};
    use std::str::FromStr;

    pub struct Reader {
        input: Stdin,
        stack: Vec<String>,
    }

    impl Reader {
        pub fn new() -> Self {
            Reader {
                input: stdin(),
                stack: vec![],
            }
        }

        pub fn read_by<F>(&mut self, count: usize) -> Vec<F>
        where
            F: FromStr,
            <F as FromStr>::Err: Debug,
        {
            let mut v = vec![];
            for _ in 0..count {
                v.push(self.read());
            }
            return v;
        }

        pub fn read<F>(&mut self) -> F
        where
            F: FromStr,
            <F as FromStr>::Err: Debug,
        {
            if self.stack.is_empty() {
                let mut line = self.read_line();
                self.stack.append(&mut line);
                self.stack.reverse();
            }
            self.stack.pop().unwrap().parse().unwrap()
        }

        fn read_line(&mut self) -> Vec<String> {
            let mut buf = String::new();
            self.input.read_line(&mut buf).unwrap();
            buf.split_whitespace().map(|s| s.to_string()).collect()
        }
    }
}