Problem:
Score : 100 points

Problem Statement

AtCoder Inc. holds a contest every Saturday.

There are two types of contests called ABC and ARC, and just one of them is held at a time.

The company holds these two types of contests alternately: an ARC follows an ABC and vice versa.

Given a string S representing the type of the contest held last week, print the string representing the type of the contest held this week.

Constraints

S is ABC or ARC.

Input

Input is given from Standard Input in the following format:

S

Output

Print the string representing the type of the contest held this week.

Sample Input 1

ABC

Sample Output 1

ARC

They held an ABC last week, so they will hold an ARC this week.

Solution in Ruby (2.7.1) (judge verdict: Accepted)

def input_n
  gets.to_i               # 単一整数
end

def input_s
  gets.chomp              # 文字列。chompを付けないと改行文字がついてくる
end

def input_a
  gets.split.map(&:to_i)  # スペースで区切られた複数の整数
end

def input_o(num)
  num.times.map { gets.to_i }  # 縦に並んだ複数の整数。たまにある
end

def output_f(num)
  puts sprintf("%.12f", num)
end

s = input_s

if s == "ABC"
  puts "ARC"
else
  puts "ABC"
end