AtCoder Regular Contest 117
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Problem Statement
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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.
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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:
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Here, we place blocks one by one from bottom to top as follows:
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- 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.
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What will be the color of the block at the top?
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Constraints
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$N$is an integer satisfying$2 \leq N \leq 400000$.- Each of
$c_1, c_2, \dots, c_N$isB,W, orR.
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Input
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Input is given from Standard Input in the following format:
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N
c_1c_2\cdotsc_N翻译中…
Output
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If the topmost block will be blue, print B; if it will be white, print W; if it will be red, print R.
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样例
Input #1
3
BWR
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`.
Input #2
4
RRBB
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`.
Input #3
6
BWWRBW
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.
Input #4
8
WWBRBBWB
Output #4
R
The figure below shows the final arrangement of blocks. The block at the top will be red; we should print `R`.
Input #5
21
BWBRRBBRWBRBBBRRBWWWR
Output #5
B
题目信息
题面与样例版权归 AtCoder 及出题人所有；中文翻译由 AI 生成（CI 管线），如有出入请以原文为准。