#include <stdio.h>

int	main()
{
	int K, A, B;

	scanf("%d\n%d %d\n", &K, &A, &B);
	for (int i = A; i <= B; i++)
	{
		if (i % K == 0){
			printf("OK\n");
			return 0;}
	}
	printf("NG\n");
	return 0;
}