import java.util.Scanner;
class Main{
  public static void main (String[] args){
    Scanner stdIn = new Scanner(System.in);
    
    int K = stdIn.nextInt();
    int a = stdIn.nextInt();
    int b = stdIn.nextInt();
    
    int t = 0;
    for(int i = a;i <= b;i++){
		 if(i % K == 0)
           t++;
    }
    if(t > 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