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 C++ (GCC 9.2.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;
#define SPACE << " " <<
#define EXCEPTERROR cout << "-1" << endl;
#define rep(k,n)    for(int i=k; i<n;  i++)
#define rep2(k,n)   for(int j=k; j<n;  j++)
#define _for(a,b,c) for(ll  i=a; i<b;  i+=c)
#define INF 1000000000000 //10^12
#define MOD 10000007 //10^9+7
#define ll long long
#define pb pop_back
template<typename T> inline void chMin(T* a, T* b) {if(*a>*b) *a=*b;}
template<typename T> inline void chMax(T* a, T* b) {if(*a<*b) *a=*b;}
template<typename T> inline int  divUp(T a, T b)   {return (a+(b-1)/b);}
int main(void){
    string s;
    cin >> s;
    cout << (s=="ABC"? "ARC":"ABC") << endl;
    return 0;
}