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>
#define FOR(i, a, n) for(int (i) = (int)(a); (i) < (int)(n); ++(i))
#define FORe(i, a, n) for(int (i) = (int)(a); (i) <= (int)(n); ++(i))
#define rFOR(i, a, n) for(int (i) = (int)(n)-1; (i) >= (int)(a); --(i))
#define rFORe(i, a, n) for(int (i) = (int)(n); (i) >= (int)(a); --(i))
#define REP(i, n) FOR((i), 0, (n))
#define REPe(i, n) FORe((i), 1, (n))
#define REPo(i, n) FORe((i), 0, (n))
#define rREP(i, n) rFOR((i), 0, (n))
#define rREPe(i, n) rFORe((i), 1, (n))
#define rREPo(i, n) rFORe((i), 0, (n))
#define rep(i, n) FOR((i), 0, (n))
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define fi first
#define se second
#define dup(x, y) (((x)+(y)-1)/(y))
#define vc(T) vector<T>
#define vv(T) v(v(T))
using namespace std;
using ll = long long;
using P = pair<int,int>;
using T = tuple<int,int,int>;
using vi = vector<int>;
using vvi = vector<vi>;
using vl = vector<ll>;
using vs = vector<string>;
using vp = vector<P>;
using vt = vector<T>;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

int main() {
  string s;
  cin >> s;
  if (s=="ABC") cout << "ARC" << endl;
  else cout << "ABC" << endl;

  return 0;
}