//package atcoder;
 
import java.util.*;
 
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();
		int count = 0;
		for(int i=A;i<B+1;i++) {
			if(i%K == 0) {
				count ++;
			}
		}
		if(count>0) {
			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