//WeLoveGolf.java
import java.util.Scanner;
class Main
{
	public static void main(String args[])
	{
		Scanner sc=new Scanner(System.in);
		int k=sc.nextInt();
        int a=sc.nextInt();
        int b=sc.nextInt();

        int sum=b/k;
        int ans=k*sum;
        //System.out.println("sum"+sum);
        //System.out.println("ans"+ans);

        if(ans>=a){
            System.out.println("OK");
        }
        else{
            System.out.println("NG");
        }
        sc.close();
    }
}
/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