JOIN

 Problem Statement

Problem Statement for AB

### Problem Statement

You are given two ints: N and K. Lun the dog is interested in strings that satisfy the following conditions:

• The string has exactly N characters, each of which is either 'A' or 'B'.
• The string s has exactly K pairs (i, j) (0 <= i < j <= N-1) such that s[i] = 'A' and s[j] = 'B'.

If there exists a string that satisfies the conditions, find and return any such string. Otherwise, return an empty string.

### Definition

 Class: AB Method: createString Parameters: int, int Returns: String Method signature: String createString(int N, int K) (be sure your method is public)

### Constraints

-N will be between 2 and 50, inclusive.
-K will be between 0 and N(N-1)/2, inclusive.

### Examples

0)

 `3` `2`
`Returns: "ABB"`
 This string has exactly two pairs (i, j) mentioned in the statement: (0, 1) and (0, 2).
1)

 `2` `0`
`Returns: "BA"`
 Please note that there are valid test cases with K = 0.
2)

 `5` `8`
`Returns: ""`
 Five characters is too short for this value of K.
3)

 `10` `12`
`Returns: "BAABBABAAB"`
 Please note that this is an example of a solution; other valid solutions will also be accepted.

This problem statement is the exclusive and proprietary property of TopCoder, Inc. Any unauthorized use or reproduction of this information without the prior written consent of TopCoder, Inc. is strictly prohibited. (c)2010, TopCoder, Inc. All rights reserved.

This problem was used for:
Single Round Match 648 Round 1 - Division I, Level One