Kan? Jigor? was the founder of judo. Judo was the first Japanese martial art to gain widespread international recognition, and the first to become an official Olympic sport. Pedagogical innovations attributed to Kan? include the use of black and white belts, and the introduction of dan ranking to show the relative ranking between members of a martial art style. Well-known mottoes attributed to Kan? include "Maximum Efficiency with Minimum Effort" and "Mutual Welfare and Benefit."