import java.util.*;
public 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 c=k;
		int flag=0;
		
		while(c<=b){
			
			if(a<=c && c<=b){
				System.out.println("OK");
				System.exit(0);
				
			}
			c+=k;
			
		}
		//System.out.println(c);
		System.out.println("NG");
		
		

		
	}
	
}

/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