번호	제목
6615	콜라츠 추측
6616	문자열 암호화
6617	Mine the Gradient
6618	Invasion
6619	Intergalactic Mortgage
6620	Simple Polygon
6621	Ambiguous Result
6622	Domino tiling
6623	Arbitrage?
6624	Bus Schedules
6625	Bus Clock Display
6626	Measuring Problem Difficulty
6627	The Easiest Problem is This One
6628	Prohibición de fumar
6629	Pyramid Guards
6630	Hack around the Lock
6631	God Save the i-th Queen
6632	Arable Area
6633	Clock Captcha
6634	Digital Display