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LEXBRAC - Bracket Sequence |
Correct Bracket Sequence (CBS) is a sequence that can be obtained through following rules:
- An empty string is a CBS.
- If A is a CBS, then B = (A) is also a CBS.
- If A is a CBS, then B = [A] is also a CBS.
- If A and B are CBS, then C = AB is also a CBS.
Length of the CBS is the number of brackets in it, and this number is always even.
Assume that '(' < ')' < '[' < ']'.
CBS a1a2 ... an is lexicographically smaller than the CBS b1b2 ... bn if and only if there exists an integer i, i <= n, so that aj=bj, for each j, 1 <= j < i and ai < bi.
Illustration
Enumerate all CBS length 4 in lexicographical order: (()), ()(), ()[], ([]), [()], [[]], [](), [][].
Task
Your task is to find k-th CBS with length n in lexicographical order.
Input
Contains 2 integers n (2 .. 250) and k (1 .. 10^120)
Output
Print the k-th CBS with length n in lexicographical order.
Example
Input: 4 3 Output: ()[]
Added by: | Chinh Nguyen |
Date: | 2008-01-10 |
Time limit: | 1s |
Source limit: | 50000B |
Memory limit: | 1536MB |
Cluster: | Cube (Intel G860) |
Languages: | All except: ERL JS-RHINO NODEJS PERL6 VB.NET |