using System;
using System.Linq;
using System.Collections.Generic;

namespace Contest
{
  class Program
  {
    static void Main(string[] args)
    {
      ABC104.A();
    }
    class ABC104
    {
      public static void A()
      {
        var R = Read.Int();
        Console.WriteLine(R < 1200 ? "ABC" : R < 2800 ? "ARC" : "AGC");
      }
      public static void B()
      {
        var S = Read.Str();
        if (S[0] != 'A') { Console.WriteLine("WA"); return; }
        if (!S.Substring(2, S.Length - 3).Contains('C')) { Console.WriteLine("WA"); return; }
        var rep = S.Replace("A", "").Replace("C", "");
        if (rep.Length != S.Length - 2) { Console.WriteLine("WA"); return; }
        if (rep != rep.ToLower()) { Console.WriteLine("WA"); return; }
        Console.WriteLine("AC");
      }
      public static void C()
      {
        var D = Read.Int();
        var G = Read.Int();
        var PC = Read.TupleInt(D);
        var dp = new long[D + 1, D * 100 + 1];
        for(int d = 0; d < D; ++d)
        {
          var P = PC[d].Item1;
          var C = PC[d].Item2;
          for (int p = 0; p <= P; ++p)
          {
            var g = (d + 1) * p * 100 + (p == P ? C : 0);
            for(int i = 0; i <= d * 100; ++i)
            {
              dp[d + 1, i + p] = Math.Max(dp[d + 1, i + p], dp[d, i] + g);
            }
          }
        }
        for(int i = 0; i <= D * 100; ++i)
        {
          if (dp[D, i] >= G) { Console.WriteLine(i); return; }
        }
      }
      public static void D()
      {
        var str = Read.Str();
        var N = str.Length;
        var dp = new long[N + 1, 4];
        dp[0, 0] = 1;
        for (int i = 0; i < N; ++i)
        {
          var c = str[i];
          dp[i + 1, 0] = (dp[i, 0] * (c == '?' ? 3 : 1)) % Util.P;
          dp[i + 1, 1] = (dp[i, 1] * (c == '?' ? 3 : 1) + (c == '?' || c == 'A' ? 1 : 0) * dp[i, 0]) % Util.P;
          dp[i + 1, 2] = (dp[i, 2] * (c == '?' ? 3 : 1) + (c == '?' || c == 'B' ? 1 : 0) * dp[i, 1]) % Util.P;
          dp[i + 1, 3] = (dp[i, 3] * (c == '?' ? 3 : 1) + (c == '?' || c == 'C' ? 1 : 0) * dp[i, 2]) % Util.P;
        }
        Console.WriteLine(dp[N, 3]);
      }
    }

    class Util
    {
      public static long[] ASum(long[] array)
      {
        var res = new long[array.Length + 1];
        for (int i = 0; i < array.Length; ++i)
        {
          res[i + 1] = res[i] + array[i];
        }
        return res;
      }
      public static long[,] ASum(long[,] matrix)
      {
        var N = matrix.GetLength(0);
        var M = matrix.GetLength(1);
        var res = new long[N + 1, M + 1];
        for(int i = 0; i < N; ++i)
        {
          for(int j = 0; j < M; ++j)
          {
            res[i + 1, j + 1] = res[i, j + 1] + res[i + 1, j] - res[i, j] + matrix[i, j];
          }
        }
        return res;
      }
      public static Dictionary<T, long> Frequency<T>(T[] array)
      {
        var dict = new Dictionary<T, long>();
        foreach (var a in array)
        {
          if (!dict.ContainsKey(a)) { dict.Add(a, 0); }
          dict[a]++;
        }
        return dict;
      }

      public static readonly long P = 1000000007;
      public static T[,] Gen<T>(int r, int c, T v)
      {
        var matrix = new T[r, c];
        for (int i = 0; i < r; ++i)
        {
          for (int j = 0; j < c; ++j)
          {
            matrix[i, j] = v;
          }
        }
        return matrix;
      }

    }

    static class Read
{
static Queue<string> queue = new Queue<string>();
static void Enqueue() { var ss = Console.ReadLine().Split(' '); foreach (var s in ss) { queue.Enqueue(s); } }
public static int Int() { if (queue.Count == 0) { Enqueue(); } return Convert.ToInt32(queue.Dequeue()); }
public static long Long() { if (queue.Count == 0) { Enqueue(); } return Convert.ToInt64(queue.Dequeue()); }
public static string Str() { if (queue.Count == 0) { Enqueue(); } return queue.Dequeue(); }
public static int[] IntN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToInt32(s)).ToArray(); }
public static long[] LongN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToInt64(s)).ToArray(); }
public static ulong[] ULongN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToUInt64(s)).ToArray(); }
public static string[] StrN() { return Console.ReadLine().Split(' '); }
public static Tuple<int, int>[] TupleInt(int n) { List<Tuple<int, int>> list = new List<Tuple<int, int>>(); for (int i = 0; i < n; ++i) { var ab = Read.IntN(); list.Add(new Tuple<int, int>(ab[0], ab[1])); } return list.ToArray(); }
public static Tuple<long, long>[] TupleLong(int n) { List<Tuple<long, long>> list = new List<Tuple<long, long>>(); for (int i = 0; i < n; ++i) { var ab = Read.LongN(); list.Add(new Tuple<long, long>(ab[0], ab[1])); } return list.ToArray(); }
public static Tuple<string, string>[] TupleStr(int n) { List<Tuple<string, string>> list = new List<Tuple<string, string>>(); for (int i = 0; i < n; ++i) { var ab = Read.StrN(); list.Add(new Tuple<string, string>(ab[0], ab[1])); } return list.ToArray(); }
public static Tuple<double, double>[] TupleDouble(int n) { List<Tuple<double, double>> list = new List<Tuple<double, double>>(); for (int i = 0; i < n; ++i) { var ab = Read.LongN(); list.Add(new Tuple<double, double>(ab[0], ab[1])); } return list.ToArray(); }
public static long[,] LongMatrix(int r, int c) { var mat = new long[r, c]; for (int i = 0; i < r; ++i) { var x = Read.LongN(); for (int j = 0; j < c; ++j) { mat[i, j] = x[j]; } } return mat; }
public static Dictionary<int, HashSet<int>> AdjacencyList(int N, int M, bool isDirectional = false)
{
Dictionary<int, HashSet<int>> dict = new Dictionary<int, HashSet<int>>();
for (int i = 0; i <= N; ++i) { dict.Add(i, new HashSet<int>()); }
        for (int i = 0; i < M; ++i) { var ab = Read.IntN(); if (!dict[ab[0]].Contains(ab[1])) { dict[ab[0]].Add(ab[1]); } if (!isDirectional && !dict[ab[1]].Contains(ab[0])) { dict[ab[1]].Add(ab[0]); } }
        return dict;
}
public static Dictionary<int, Dictionary<int, long>> AdjacencyListWithWeight(int N, int M)
{
Dictionary<int, Dictionary<int, long>> dict = new Dictionary<int, Dictionary<int, long>>(); for (int i = 0; i <= N; ++i) { dict.Add(i, new Dictionary<int, long>()); }
for (int i = 0; i < M; ++i) { var ab = Read.IntN(); dict[ab[0]].Add(ab[1], ab[2]); dict[ab[1]].Add(ab[0], ab[2]); }
return dict;
}
}
    }
}


Measured memory_bytes: 11220