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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using BitArray = System.Collections.BitArray;
using BigInteger = System.Numerics.BigInteger;
using TextReader = System.IO.TextReader;

namespace AtCoderProject
{
    public class Program
    {
        public object Calc()
        {
            var n = consoleReader.Int;
            return n < 1200 ? "ABC" : n < 2800 ? "ARC" : "AGC";
        }

        #region いつもの
        private readonly ConsoleReader consoleReader;
        public Program(ConsoleReader consoleReader) { this.consoleReader = consoleReader; }
        static void Main() => Console.WriteLine(new Program(new ConsoleReader(Console.In)).Calc()); static string AllLines<T>(IEnumerable<T> source) => string.Join("\n", source);
        #endregion
    }

#pragma warning disable
    public class ConsoleReader
    {
        private string[] line = Array.Empty<string>();
        private int linePosition;
        private TextReader textReader;
        public ConsoleReader(TextReader tr) { textReader = tr; }
        public int Int => int.Parse(String);
        public long Long => long.Parse(String);
        public double Double => double.Parse(String);
        public string String
        {
            get
            {
                if (linePosition >= line.Length)
                {
                    linePosition = 0;
                    line = textReader.ReadLine().Split();
                }
                return line[linePosition++];
            }
        }
        public class SplitLine
        {
            private string[] splited;
            public SplitLine(ConsoleReader cr) { splited = cr.textReader.ReadLine().Split(); }
            public int[] Int => String.Select(x => int.Parse(x)).ToArray();
            public long[] Long => String.Select(x => long.Parse(x)).ToArray();
            public double[] Double => String.Select(x => double.Parse(x)).ToArray();
            public string[] String => splited;
        }
        public SplitLine Split => new SplitLine(this);
        public class RepeatReader
        {
            ConsoleReader cr; int count;
            public RepeatReader(ConsoleReader cr, int count) { this.cr = cr; this.count = count; }
            public IEnumerable<T> Select<T>(Func<ConsoleReader, T> func) { for (int i = 0; i < count; i++) yield return func(cr); }
            public IEnumerable<string> String { get { for (int i = 0; i < count; i++) yield return cr.String; } }
            public IEnumerable<int> Int { get { for (int i = 0; i < count; i++) yield return cr.Int; } }
            public IEnumerable<double> Double { get { for (int i = 0; i < count; i++) yield return cr.Double; } }
        }
        public RepeatReader Repeat(int count) => new RepeatReader(this, count);
    }
}