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