import java.util.Scanner;
class Main{
public static void main(String[] args){
 Scanner scan = new Scanner(System.in);
 
 int K = scan.nextInt();
 int A = scan.nextInt();
 int B = scan.nextInt();
 int count = 0;
  
  for (int i = 0; i < B-A+1; i++){
  	if ((A + i) % K == 0){
      count += 1;
    }
    else{
    }
  }
  if (count > 0){
  System.out.println("OK");
  }
  if (count == 0){
    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