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 = 0;
      for(int i=A;i<B+1;i++){
        if(i%K==0){
          C=C+1;
          break;
        }else{
          continue;
        }
      }if(C>0){
        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