A balanced bracket sequence is a string consisting only of the characters "(
" (opening brackets) and ")
" (closing brackets) such that each opening bracket has a "matching" closing bracket, and vice versa. For example, "(())()
" is a balanced bracket sequence, whereas "(())(()
" and "())(()
" are not.
Given two bracket sequences A and B of the same length, we say that A is lexicographically smaller than B (and write A < B) if:
(
", and B has a ")
" in the left-most position in which A and B differFor example "(())()
" < "()()()
" because they first differ in the second position from the left, and the first string has an "(
" in that position, whereas the second string has a ")
". For a given length N, the "<" operator defines an ordering on all balanced bracket sequences of length N. For example, the ordering of the sequences of length 6 is:
((()))
(()())
(())()
()(())
()()()
Given a length N and a positive integer M, your task is to find the Mth balanced bracket sequence in the ordering.
You will be given an even integer N (2 ≤ N ≤ 2000), and a positive integer M. It is guaranteed that M will be no more than 1018 and no more than the number of balanced bracket sequences of length N (whichever is smaller).
Output the Mth balanced bracket sequence of length N, when ordered lexicographically.
6 4
()(())