A. Secret Sport
time limit per test
3 seconds
memory limit per test
512 megabytes
input
standard input
output
standard output

Let's consider a game in which two players, A and B, participate. This game is characterized by two positive integers, $$$X$$$ and $$$Y$$$.

The game consists of sets, and each set consists of plays. In each play, exactly one of the players, either A or B, wins. A set ends exactly when one of the players reaches $$$X$$$ wins in the plays of that set. This player is declared the winner of the set. The players play sets until one of them reaches $$$Y$$$ wins in the sets. After that, the game ends, and this player is declared the winner of the entire game.

You have just watched a game but didn't notice who was declared the winner. You remember that during the game, $$$n$$$ plays were played, and you know which player won each play. However, you do not know the values of $$$X$$$ and $$$Y$$$. Based on the available information, determine who won the entire game — A or B. If there is not enough information to determine the winner, you should also report it.

Input

Each test contains multiple test cases. The first line contains a single integer $$$t$$$ $$$(1 \leq t \leq 10^4)$$$ - the number of test cases. The description of the test cases follows.

The first line of each test case contains an integer $$$n$$$ $$$(1 \leq n \leq 20)$$$ - the number of plays played during the game.

The second line of each test case contains a string $$$s$$$ of length $$$n$$$, consisting of characters $$$\texttt{A}$$$ and $$$\texttt{B}$$$. If $$$s_i = \texttt{A}$$$, it means that player A won the $$$i$$$-th play. If $$$s_i = \texttt{B}$$$, it means that player B won the $$$i$$$-th play.

It is guaranteed that the given sequence of plays corresponds to at least one valid game scenario, for some values of $$$X$$$ and $$$Y$$$.

Output

For each test case, output:

  • $$$\texttt{A}$$$ — if player A is guaranteed to be the winner of the game.
  • $$$\texttt{B}$$$ — if player B is guaranteed to be the winner of the game.
  • $$$\texttt{?}$$$ — if it is impossible to determine the winner of the game.
Example
Input
7
5
ABBAA
3
BBB
7
BBAAABA
20
AAAAAAAABBBAABBBBBAB
1
A
13
AAAABABBABBAB
7
BBBAAAA
Output
A
B
A
B
A
B
A
Note

In the first test case, the game could have been played with parameters $$$X = 3$$$, $$$Y = 1$$$. The game consisted of $$$1$$$ set, in which player A won, as they won the first $$$3$$$ plays. In this scenario, player A is the winner. The game could also have been played with parameters $$$X = 1$$$, $$$Y = 3$$$. It can be shown that there are no such $$$X$$$ and $$$Y$$$ values for which player B would be the winner.

In the second test case, player B won all the plays. It can be easily shown that in this case, player B is guaranteed to be the winner of the game.

In the fourth test case, the game could have been played with parameters $$$X = 3$$$, $$$Y = 3$$$:

  • In the first set, $$$3$$$ plays were played: AAA. Player A is declared the winner of the set.
  • In the second set, $$$3$$$ plays were played: AAA. Player A is declared the winner of the set.
  • In the third set, $$$5$$$ plays were played: AABBB. Player B is declared the winner of the set.
  • In the fourth set, $$$5$$$ plays were played: AABBB. Player B is declared the winner of the set.
  • In the fifth set, $$$4$$$ plays were played: BBAB. Player B is declared the winner of the set.

In total, player B was the first player to win $$$3$$$ sets. They are declared the winner of the game.