#include<stdio.h>
int main(void)
{
	int a,b,num = 0,k,flg = 0;
	
	scanf("%d%d%d", &k, &a, &b);

	while(1){
		num += k;

		if (num >= a && num <= b) {
			flg = 1;
			break;
		}

		if (num > 1000) {
			flg = 0;
			break;
		}
	}

	if (flg == 1) {
		printf("OK\n");
	}
	else {
		printf("NG\n");
	}

	return 0;
}