import java.util.*;

public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
        int b = sc.nextInt();
		int c = sc.nextInt();
        int d = 0;
        for (int i= b; i<= c; i++) {
          if (i % a == 0) {
       		d = 1;
            }
        }
      if (d == 0) {
        System.out.println("NG");
        } else {
        System.out.println("OK");
      }
	}
}
/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