#include <stdio.h>

int main(void) {
	int K, A, B;
	int asumi, iguti;
	if (scanf("%d", &K) != 1) return 1;
	if (scanf("%d%d", &A, &B) != 2) return 1;
	asumi = A / K;
	iguti = B / K;
	if (asumi < iguti) {
		puts("OK");
	} else {
		puts(A % K == 0 ? "OK" : "NG");
	}
	return 0;
}
