#include <stdio.h>

int main()
{
	int k;
	int a;
	int b;

	scanf("%d", &k);
	scanf("%d %d", &a, &b);
	while (a <= b)
	{
		if (a % k == 0)
		{
			printf("OK\n");
			return;
		}
		a++;
	}
	printf("NG\n");
  	return;
}