#include<stdio.h>

int main(){
	int k, K;
	scanf("%d", &K);
	int A, B;
	scanf("%d %d", &A, &B);
	if(K <= B - A + 1)
		printf("OK");
	else{
		for(k = A; k <= B; k++){
			if(k % K == 0){
				printf("OK");
				break;
			}
		}
		if(k == B + 1)
			printf("NG");
	}
	return 0;
}