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 divide = a/k;
      if (a%k==0) {System.out.println("OK");}
      else if (((divide+1)*k) <= b)
      {System.out.println("OK");}
      else {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