a happy string string thatconsist letter set b csi si 1 value 1 slength 1 string 1indexedfor example string abc ac b abcbabcbcb happy string string aa baa ababbc happy stringsGiven integer n k consider list happy string length n sort lexicographical orderreturn kth string list return string k happy string length n Example 1input n 1 k 3output cExplanation the list b c contain happy string length 1 the string cExample 2input n 1 k 4Output Explanation there 3 happy string length 1example 3input n 3 k 9output cabexplanation there 12 different happy string length 3 aba abc aca acb bab bac bca bcb cab cac cba cbc you find 9th string cab Constraints1 n 101 k 100