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 Kotlin (1.3.71) (judge verdict: Accepted)

@file:Suppress("DuplicatedCode")

import java.io.IOException
import java.io.InputStream
import java.io.PrintWriter
import java.util.NoSuchElementException

fun main() {
    PrintWriter(System.out).use { out ->
        A.solve(A.FastScanner(), out)
        out.flush()
    }
}

private fun A.solve(sc: A.FastScanner, out: PrintWriter) {
    val name = readLine()!!
    out.println(if (name == "ABC") "ARC" else "ABC")
}

@Suppress("MemberVisibilityCanBePrivate")
private object A {
    class FastScanner {
        private val `in`: InputStream = System.`in`
        private val buffer = ByteArray(1024)
        private var ptr = 0
        private var buflen = 0
        private fun hasNextByte(): Boolean {
            if (ptr < buflen) {
                return true
            } else {
                ptr = 0
                try {
                    buflen = `in`.read(buffer)
                } catch (e: IOException) {
                    e.printStackTrace()
                }
                if (buflen <= 0) {
                    return false
                }
            }
            return true
        }

        private fun readByte(): Int {
            return if (hasNextByte()) buffer[ptr++].toInt() else -1
        }

        operator fun hasNext(): Boolean {
            while (hasNextByte() && !isPrintableChar(buffer[ptr].toInt())) ptr++
            return hasNextByte()
        }

        operator fun next(): String {
            if (!hasNext()) throw NoSuchElementException()

            return buildString {
                var b = readByte()

                while (isPrintableChar(b)) {
                    appendCodePoint(b)
                    b = readByte()
                }
            }
        }

        fun nextLong(): Long {
            if (!hasNext()) throw NoSuchElementException()
            var n: Long = 0
            var minus = false
            var b = readByte()

            if (b == '-'.toInt()) {
                minus = true
                b = readByte()
            }

            if (b < '0'.toInt() || '9'.toInt() < b) {
                throw NumberFormatException()
            }

            while (true) {
                if ('0'.toInt() <= b && b <= '9'.toInt()) {
                    n *= 10
                    n += b - '0'.toInt().toLong()
                } else if (b == -1 || !isPrintableChar(b)) {
                    return if (minus) -n else n
                } else {
                    throw NumberFormatException()
                }

                b = readByte()
            }
        }

        fun nextInt(): Int {
            val nl = nextLong()
            if (nl < Int.MIN_VALUE || nl > Int.MAX_VALUE) throw NumberFormatException()
            return nl.toInt()
        }

        fun nextDouble(): Double {
            return next().toDouble()
        }

        fun readIntArray(n: Int): IntArray {
            val arr = IntArray(n)

            for (i in 0 until n) {
                arr[i] = nextInt()
            }

            return arr
        }

        companion object {
            private fun isPrintableChar(c: Int): Boolean {
                return c in 33..126
            }
        }
    }
}