the difference easy hard version constraintsA subsequence string derive string delete symbol change order remain symbol Characters delete require successively gap for example stre abaca follow string subsequence abaca aba aaa string but follow string subsequence aabaca cb bcaayou give string s consist n lowercase latin lettersin subsequence t give string add set S the set s can not contain duplicate this cost n t t length add subsequence ie price equal number delete charactersYour task find minimum possible total cost obtain set S size k report impossible