#include<stdio.h>

int main(void) {
	int k, a, b, i, frg = 0;

	scanf("%d", &k);
	scanf("%d %d", &a,&b);

	for (i = a; i <= b; i++) {
		if (i%k == 0) {
			frg = 1;
			break;
		}
	}
	if(frg==1) printf("OK\n");
	else printf("NG\n");

	return 0;
}