Problem Statement

We have N blocks arranged in a row, where each block is painted blue, white, or red.
The color of the i-th block from the left $(1 \leq i \leq N)$ is represented by a character c_i; B, W, and R stand for blue, white, and red, respectively.
From this situation, we will pile up blue, white, and red blocks to make a pyramid with N steps. The following figure shows an example of this:

Here, we place blocks one by one from bottom to top as follows:

• if the two blocks immediately below a position have the same color, we will place there a block of the same color;
• if the two blocks immediately below a position have different colors, we will place there a block of the color different from those two colors.

What will be the color of the block at the top?

Input

Input is given from Standard Input in the following format:
N
$c_1c_2\cdotsc_N$

Output

If the topmost block will be blue, print B; if it will be white, print W; if it will be red, print R.

Constraints

• N is an integer satisfying $2 \leq N \leq 400000$.
• Each of $c_1, c_2, \dots, c_N$ is B, W, or R.

Sample Input 1

3
BWR

Sample Output 1

W

In this case, we will pile up blocks as follows:

• the 1-st and 2-nd blocks from the left in the bottom row are respectively blue and white, so we place a red block on top of it;
• the 2-nd and 3-rd blocks from the left in the bottom row are respectively white and red, so we place a blue block on top of it;
• the blocks in the 2-nd row from the bottom are respectively red and blue, so we place a white block on top of it.

Thus, the block at the top will be white; we should print W.

Sample Input 2

4
RRBB

Sample Output 2

W

In this case, we will pile up blocks as follows:

• the 1-st and 2-nd blocks from the left in the bottom row are both red, so we place a red block on top of it;
• the 2-nd and 3-rd blocks from the left in the bottom row are respectively red and blue, so we place a white block on top of it;
• the 3-rd and 4-th blocks from the left in the bottom row are both blue, so we place a blue block on top of it;
• the 1-st and 2-nd blocks from the left in the 2-nd row from the bottom are respectively red and white, so we place a blue block on top of it;
• the 2-nd and 3-rd blocks from the left in the 2-nd row from the bottom are respectively white and blue, so we place a red block on top of it;
• the blocks in the 3-rd row from the bottom are respectively blue and red, so we place a white block on top of it.

Thus, the block at the top will be white; we should print W.

Sample Input 3

6
BWWRBW

Sample Output 3

B

The figure below shows the final arrangement of blocks. The block at the top will be blue; we should print B.

Note that this is the case shown as an example in Problem Statement.

Sample Input 4

8
WWBRBBWB

Sample Output 4

R

The figure below shows the final arrangement of blocks. The block at the top will be red; we should print R.

Sample Input 5

21
BWBRRBBRWBRBBBRRBWWWR

Sample Output 5

B

见题面 Input 部分

见题面 Output 部分