import java.util.*;
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 ans=false;
        for (int d=a;d<=b;d++){
            if(d%k==0){
                ans=true;
                break;
            }
        }
        if(ans){
            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