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)

//I am so vegetable
#pragma GCC optimize(2)
#include <bits/stdc++.h>
#define FIO ios::sync_with_stdio(false), cin.tie(0), cout.tie(0)
#define PB push_back
#define IN insert
#define ER erase
#define CT count
#define EP empty
#define _for(i,a,b) for(int i = (a);i<(b);++i)
#define _rfor(i,a,b) for(int i = (a);i>(b);--i)
#define _sfor(p,st) for(auto &p:st)
using namespace std;
typedef long long ll;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9+7;
const double eps = 1e-6;
const double pi = 3.141593;
int gcd(int a, int b) { return b == 0 ? a : gcd(b, a % b); }
ll qpow(ll x, ll y) { ll ans = 1; for (; y > 0; y >>= 1) { if (y & 1)ans *= x; x *= x; }return ans; }
ll qpow(ll x, ll y, int MOD) { ll ans = 1; for (; y > 0; y >>= 1) { if (y & 1)ans = ans*x%MOD; x = x*x%MOD; }return ans; }
void exgcd(ll a,ll b,ll &x,ll &y){
    if(!b){x=1;y=0;return;}
    exgcd(b,a%b,x,y);
    ll X=x;
    x=y; y=X-a/b*y;
}
ll inv(ll x, int mod = MOD) { return qpow(x, mod - 2) % mod; }
ll m_m(ll a){ return (a%MOD+MOD)%MOD; }

int main() {
	//ofstream cout("E:\\acm dream\\out.txt",ios::out);
	FIO;
    string s;cin>>s;
    if(s=="ABC")cout<<"ARC";
    else cout<<"ABC";
	return 0;
}