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 JavaScript (Node.js 12.16.1) (judge verdict: Accepted)

"use strict";
var input = require("fs").readFileSync("/dev/stdin", "utf8");
var cin = input.split(/ |\n/), cid = 0;
function next(a) { return a ? cin[cid++] : +cin[cid++]; }
function nexts(n, a) { return a ? cin.slice(cid, cid += n) : cin.slice(cid, cid += n).map(a => +a); }
function nextm(h, w, a) { var r = [], i = 0; if (a) for (; i < h; i++)r.push(cin.slice(cid, cid += w)); else for (; i < h; i++)r.push(cin.slice(cid, cid += w).map(a => +a)); return r; }
function xArray(v) { var a = arguments, l = a.length, r = "Array(a[" + --l + "]).fill().map(x=>{return " + v + ";})"; while (--l) r = "Array(a[" + l + "]).fill().map(x=>" + r + ")"; return eval(r); }

var myOut = main();
if (myOut !== undefined) console.log(myOut);

function main() {
    var s = next(1);
    return s === "ABC" ? "ARC" : "ABC";
}
// 2422824228の場合
// s[i]...8,  2,   2,    4,                         2
// k......1, 10, 100, 1000,           10000%2019=1924, 10万%2019=19240%2019=1069
// x......8, 28, 228, 4228%2019=0190, 20190%2019=2924*2+190=4038=0