#include<stdio.h>
int main(void) {
	int a=0;
	scanf("%d", &a);
	int b = 0;
	int c = 0;
	int d = 0;
	scanf("%d %d", &b, &c);
	for (i = b; i <= c; i++) {
		if (i % a == 0)
			d = 1;
	}
	if (d == 1)
		printf("OK");
	else
		printf("NG");
}