Don't use HashSet for small amount.
Don't use HashSet for small amount.

smoogipooo/osu-framework,peppy/osu-framework,smoogipooo/osu-framework,ZLima12/osu-framework,EVAST9919/osu-framework,ppy/osu-framework,EVAST9919/osu-framework,EVAST9919/osu-framework,peppy/osu-framework,ZLima12/osu-framework,ppy/osu-framework,peppy/osu-framework,ppy/osu-framework,EVAST9919/osu-framework