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 <iostream>
#include <bits/stdc++.h>
#define ll long long
#define pb push_back
#define ff first
#define ss second
#define MOD 1000000007
using namespace std;


unordered_map<ll,ll> m,m2;
unordered_map<ll,vector<ll>> m3;
vector<ll> v,v1;
ll flag; 

ll dfs(ll a)
{
         ll i,j,sum;
         j=0;
         sum=0;
         for(i=0;i<m3[a].size();i++)
          {
              j=m3[a][i];
              if(m.find(j)==m.end())
              {
                  if(m[a]==1)
                  {
                       m[j]=-1;
                       v.push_back(j);
                       dfs(j);
                  }
                  else
                  {
                      m[j]=1;
                      v1.push_back(j);
                      dfs(j);
                  }
              }
              if(m[a]==m[j])
              {
                  cout<<-1;
                  exit(0);
              }
          }
          return i;
}

int main()
{
    ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
    long long int i,j,a,b,n,x,y,z,t,k,sum,sum1;
  //  vector<long long int> v,v1;
    string s,s1;
   // unordered_map<long long int,long long int> m,m1;
  //  unordered_map<long long int,vector<long long int>> m3;
    t=1;
   // cin>>t;
    while(t--)
    {
       cin>>s;
       if(s=="ABC")
       {
           cout<<"ARC";
       }
       else
       {
           cout<<"ABC";
       }
       
    }
}