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)

/*
 * main.c
 *
 *  Created on: 2020/03/28
 *      Author: family
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#define MAX(a,b) (a > b ? a : b)
#define MIN(a,b) (a > b ? b : a)
typedef long long int ll;
typedef unsigned long long int ull;

int sort_inc(const void *a, const void *b) { return (*(int*)a - *(int*)b);}
int sort_dec(const void* a, const void* b) { return (*(int*)b - *(int*)a);}
int sort_dec_ll(const void *a, const void *b) {
    ll da = *(ll*)a, db = *(ll*)b;    int val = 0;
    if(da > db) { val = -1; }
    else if (da == db) { val = 0; }
    else { val = 1; }
    return val;
}
int sort_inc_ll(const void *a, const void *b) {
    ll da = *(ll*)a, db = *(ll*)b;    int val = 0;
    if(da > db) { val = 1; }
    else if (da == db) { val = 0; }
    else { val = -1; }
    return val;
}
int sort_dic(const void *a, const void *b) {
    char *pa = (char *)a;    char *pb = (char *)b;    int i = 0, val = 0, N = 10;
    for (i = 0; i < N; i++) {
    	char da = pa[i], db = pb[i];
    	if (da == db) continue;
  		if (da > db) val = 1; else val = -1;
        break;
    }
    return val;
}

void yesno(int ans) {
	if (ans == 1) {	printf("Yes\n");
	} else {		printf("No\n");	}
	return;
}

void okng(int ans) {
	if (ans == 1) { printf("OK\n");
	} else { 		printf("NG\n");	}
	return;
}

int main()
{
	char S[4] = {0};
	scanf("%s", S);

	if (S[1] == 'B') {
		printf("ARC\n");
	} else {
		printf("ABC\n");
	}
	return 0;
}