import java.io.*;
import java.util.*;
public class Main
{
    static PrintWriter out=new PrintWriter((System.out));
    public static void main(String args[])throws IOException
    {
        Reader sc=new Reader();
        int k=sc.nextInt();
        int n=sc.nextInt();
        int m=sc.nextInt();
        boolean found=false;
        for(int x=n;x<=m;x++)
        {
            if(x%k==0)
            {
                found=true;
                break;
            }
        }
        out.println(found?"OK":"NG");
        out.close();
    }
 
    public static void solve()
    {
    }
 
    static class Reader 
    { 
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer("");
        public String next()
        {
            while(!st.hasMoreTokens())
            {
                try
                {
                    st=new StringTokenizer(br.readLine());
                }
                catch(Exception e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
 
        public int nextInt()
        {
            return Integer.parseInt(next());
        }
 
        public long nextLong()
        {
            return Long.parseLong(next());
        }
 
        public double nextDouble()
        {
            return Double.parseDouble(next());
        }
 
        public String nextLine()
        {
            try
            {
                return br.readLine();
            }
            catch(Exception e)
            {
                e.printStackTrace();
            }
            return null;
        }
 
        public boolean hasNext()
        {
            String next=null;
            try
            {
                next=br.readLine();
            }
            catch(Exception e)
            {
            }
            if(next==null)
            {
                return false;
            }
            st=new StringTokenizer(next);
            return true;
        }
    } 
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz