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: Runtime Error)

require 'set'

N,M = gets.split.map(&:to_i)
H = [0] + gets.split.map(&:to_i)
s = Set.new(1..N)
M.times do
  a,b = gets.split.map(&:to_i)
  s.delete(a) if H[a]<=H[b]
  s.delete(b) if H[b]<=H[a]
end
puts s.size