import java.util.*;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub

		int k;
		int A;
		int B;
		  Scanner scan = new Scanner(System.in);
		  
		 // Read the next integer from the screen 
		 	k= scan.nextInt(); 
		 	
	        
	        // Read the next integer from the screen 
	        A = scan.nextInt(); 
	        
	       
	        
	        // Read the next integer from the screen 
	        B= scan.nextInt();
	        check(k,A,B);
	        }
	public static void check(int k,int A,int B)
	{
		int l=0;
		for(int i=A;i<=B;i++)
		{
			if(i%k==0)
			{
			l=1	;
			}
		}
		
		if(l==1)
		{
			System.out.print("OK");
		}
		else 
		{
			System.out.print("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