using System;
using System.Collections;
using System.Collections.Generic;
using System.IO.Pipes;
using System.Linq;
using System.Numerics;
using System.Text;
using System.Threading;

namespace ForATCODER
{
    public class Program
    {
        public static void Main(string[] args)
        {
            int k = s2i(Console.ReadLine());
            int[] a = s2iarray(Console.ReadLine().Split(' '));
            for (int i = 1; i <= int.MaxValue; i++)
            {
                int n = k * i;
                if (a[0] <= n && a[1] >= n)
                {
                    RESULT("OK");
                    return;
                }
                else if (a[1] < n) break;
            }
            RESULT("NG");

        }
        public static ulong pow(int a, int b)
        {
            ulong res = 1;
            for (int i = 0; i < b; i++)
            {
                res *= (ulong)a;
            }
            return res;
        }
        public static void sortT<T>(T[] arr, int index)
        {

            // If the index is negative,  
            // it represents the bitwise 
            // complement of the next larger  
            // element in the array. 
            if (index < 0)
            {

                index = ~index;

                if (index == 0)
                    Console.Write("beginning of array");
                else
                    Console.Write("{0} and ", arr[index - 1]);

                if (index == arr.Length)
                    Console.WriteLine("end of array.");
                else
                    Console.WriteLine("{0}", arr[index]);
            }
        }







        static int s2i(String s)
        {
            return Convert.ToInt32(s);
        }
        static ulong s2l(String s)
        {
            return Convert.ToUInt64(s);
        }
        static void RESULT(double res)
        {
            Console.WriteLine(res);
        }
        static void RESULT(long res)
        {
            Console.WriteLine(res);
        }
        static void RESULT(ulong res)
        {
            Console.WriteLine(res);
        }
        static void RESULT(int res)
        {
            Console.WriteLine(res);
        }
        static void RESULT(String res)
        {
            Console.WriteLine(res);
        }
        static String[] ReadLineAll(int count)
        {
            String[] res = new String[count];
            for (int i = 0; i < count; i++)
            {
                res[i] = Console.ReadLine();
            }
            return res;
        }

        static int[] s2iarray(String[] src)
        {
            int len = src.Length;
            int[] res = new int[len];
            for (int i = 0; i < len; i++)
            {
                res[i] = Convert.ToInt32(src[i]);
            }
            return res;
        }
        static long[] s2larray(String[] src)
        {
            int len = src.Length;
            long[] res = new long[len];
            for (int i = 0; i < len; i++)
            {
                res[i] = Convert.ToInt64(src[i]);
            }
            return res;
        }
        static ulong[] s2larray2(String[] src)
        {
            int len = src.Length;
            ulong[] res = new ulong[len];
            for (int i = 0; i < len; i++)
            {
                res[i] = Convert.ToUInt64(src[i]);
            }
            return res;
        }
    }
}


Measured memory_bytes: 27560