import java.util.Scanner;

public 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 cnt = 0;
      for(int i=A; i<=B; i++){
		if(i%K == 0){
			cnt = cnt+1;
			}
		}
        if (cnt >= 1 ) {
            System.out.println("OK");
        }
        else {
            System.out.println("NG");
        }
        scan.close();
    }
}
/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