#include <stdio.h>

Int main(void) {
	Int k, a, b;
	
	scanf("%d", &k);
	Scanf("%d%d", &a, &b);
	
	Int largest = (b / k) * k;
	If (a <= largest) {
		Puts("OK");
	} else {
		Puts("NG");
	}
	Return 0;
}
