https://www.youtuberandom.com/watch/nxmgeoplE2Q&list=PLPOW4yzC55NnIgKlgcAGJ_jgf3wj0wPuZ/missing-number-series-for-sbi-po-2019-math-class-for-sbi-clerk-sbi-crash-course-day-1-for-quant-video