// Starting with the name of Allah

#include<stdio.h>
int main()
{
	int K,A,B,i,x,y,z=0;
	scanf("%d",&K);
	scanf("%d %d",&A,&B);

	for(i=A;i<=B;i++){
		if(i%K==0){
			z=2;
			break;
		}
	}
	if(z==2){
		printf("OK\n");
	}
	else{
		printf("NG\n");
	}
}
