it October 18 2017 Shohag melancholic soul strong determination pursue Competitive Programming seriously heart find fascinating Fast forward 4 year happy take road he create contest codeforce he find astounding problem idea solve help solve final problem roundyou give integer n k x Find number modulo 998244353 integer sequence a_1 a_2 ldot a_n follow condition satisfy 0 le a_i lt 2k integer 1 n there nonempty subsequence bitwise XOR element subsequence x a sequence b subsequence sequence c b obtain c deletion possibly zero element