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();
        int temp=K;
        while(B>=temp){
            if(A<=temp){
                System.out.println("OK");
                System.exit(0);
            }else{
                temp+=K;
            }
        }
        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