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();
      
      	boolean flag = false;
      	for(int i = a; i <= b; i++){
          if(i % k == 0) flag = true;
        };

      	if(flag){
          System.out.println("OK");
        }else{
          System.out.println("NG");
        };
	}
}