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 in freopen("input.txt", "r", stdin);
#define out freopen("output.txt", "w", stdout);
#define clr(arr, key) memset(arr, key, sizeof arr)
#define pb push_back
#define mp(a, b) make_pair(a, b)
#define infinity (1 << 28)
#define LL long long
#define PI acos(-1)
#define gcd(a, b) __gcd(a, b)
#define CF ios_base::sync_with_stdio(0);cin.tie(0);
#define lcm(a, b) ((a)*((b)/gcd(a,b)))
#define all(v) v.begin(), v.end()
#define no_of_ones __builtin_popcount // __builtin_popcountll for LL
#define SZ(v) (int)(v.size())
#define eps 1e-7

//int col[8] = {0, 1, 1, 1, 0, -1, -1, -1};
//int row[8] = {1, 1, 0, -1, -1, -1, 0, 1};
//int col[4] = {1, 0, -1, 0};
//int row[4] = {0, 1, 0, -1};
//int months[13] = {0, ,31,28,31,30,31,30,31,31,30,31,30,31};

using namespace std;

struct point{int x, y; point () {} point(int a, int b) {x = a, y = b;}};
template <class T> T sqr(T a){return a * a;}
template <class T> T power(T n, T p) { T res = 1; for(int i = 0; i < p; i++) res *= n; return res;}
template <class T> double getdist(T a, T b){return sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y));}    // distance between a and b
template <class T> T extract(string s, T ret) {stringstream ss(s); ss >> ret; return ret;}
template <class T> string tostring(T n) {stringstream ss; ss << n; return ss.str();}
//LL bigmod(LL B,LL P,LL M){LL R=1; while(P>0)  {if(P%2==1){R=(R*B)%M;}P/=2;B=(B*B)%M;} return R;}
struct fast{fast(){ios_base::sync_with_stdio(0);cin.tie(0);}}cincout;

#define MAX 100010
/***********************************THE GRASS IS ALWAYS GREENER ON THE OTHER SIDE***********************************/

int main()
{
    string s;
    cin >> s;
    if(s == "ABC")
        cout << "ARC";
    else
    {
        cout << "ABC";
    }
    cout << "\n";
    
    return 0;
}