import java.util.Scanner;

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();

        boolean trueCount = false;
        for(int i = A; i<=B; i++){
            if(i % K == 0){
                trueCount = true;
            }
        }
        System.out.println(trueCount == true ? "OK" : "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