Problem:
Score : 100 points

Problem Statement

A programming competition site AtCode regularly holds programming contests.

The next contest on AtCode is called ABC, which is rated for contestants with ratings less than 1200.

The contest after the ABC is called ARC, which is rated for contestants with ratings less than 2800.

The contest after the ARC is called AGC, which is rated for all contestants.

Takahashi's rating on AtCode is R. What is the next contest rated for him?

Constraints

0 ≤ R ≤ 4208

R is an integer.

Input

Input is given from Standard Input in the following format:

R

Output

Print the name of the next contest rated for Takahashi (ABC, ARC or AGC).

Sample Input 1

1199

Sample Output 1

ABC

1199 is less than 1200, so ABC will be rated.

Sample Input 2

1200

Sample Output 2

ARC

1200 is not less than 1200 and ABC will be unrated, but it is less than 2800 and ARC will be rated.

Sample Input 3

4208

Sample Output 3

AGC

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

macro_rules! input {
    // ?
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        let mut next = || { iter.next().unwrap() };
        input_inner!{next, $($r)*}
    };

    // stdinの生成 値の読み込み開始
    ($($r:tt)*) => {
        let stdin = std::io::stdin();
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
        let mut next = move || -> String{
            bytes
                .by_ref()
                .map(|r|r.unwrap() as char)
                .skip_while(|c|c.is_whitespace())
                .take_while(|c|!c.is_whitespace())
                .collect()
        };
        input_inner!{next, $($r)*}
    };
}

macro_rules! input_inner {
    // ?
    ($next:expr) => {};
    // ?
    ($next:expr, ) => {};

    // 変数名:型の読み込みの繰り返し
    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
}

macro_rules! read_value {
    // 値を読み込むベース 型,の繰り返し
    ($next:expr, ( $($t:tt),* )) => {
        ( $(read_value!($next, $t)),* )
    };

    // 配列の読み込み
    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };

    // 文字列Vec<char>の読み込み
    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };

    // usize1?の読み込み
    ($next:expr, usize1) => {
        read_value!($next, usize) - 1
    };

    // 指定した型で読み込み
    ($next:expr, $t:ty) => {
        $next().parse::<$t>().expect("Parse error")
    };
}
fn main() {
    input! {
        n: usize,
    };

    println!("{}", solve(n));
}

fn solve(r: usize) -> &'static str{
    if r < 1200 {
        return "ABC"
    }
    if r < 2800 {
        return "ARC";
    }
    return "AGC";
}

macro_rules! tests {
    ($($name:ident:[$( $args:expr ),*] => $output:expr,)*) => {
        mod tests {
            $(
                #[test]
                fn $name() {
                    assert_eq!($output,super::solve($($args),*));
                }
            )*
        }
    }
}


tests! {
    //テスト名:[引数]=>expected
    test1:[1199]=>"ABC",
    test2:[1200]=>"ARC",
    test3:[4208]=>"AGC",
}