#include <stdio.h>
 
int main(void) {
	int i,a,b,k,p=0;
	scanf("%d %d %d",&k,&a,&b);
	if(b-a>k){p=1;}
	else{
		for(i=a;i<=b;i++){
			if(i%k==0){
				p=1;
				break;
			}
		}
	}
	if(p==1){printf("OK\n");}
	else{printf("NG\n");}
	return 0;
}
 