Problem:
Score : 500 points

Problem Statement

You have a string A = A_1 A_2 ... A_n consisting of lowercase English letters.

You can choose any two indices i and j such that 1 \leq i \leq j \leq n and reverse substring A_i A_{i+1} ... A_j.

You can perform this operation at most once.

How many different strings can you obtain?

Constraints

1 \leq |A| \leq 200,000

A consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

A

Output

Print the number of different strings you can obtain by reversing any substring in A at most once.

Sample Input 1

aatt

Sample Output 1

5

You can obtain aatt (don't do anything), atat (reverse A[2..3]), atta (reverse A[2..4]), ttaa (reverse A[1..4]) and taat (reverse A[1..3]).

Sample Input 2

xxxxxxxxxx

Sample Output 2

1

Whatever substring you reverse, you'll always get xxxxxxxxxx.

Sample Input 3

abracadabra

Sample Output 3

44

Solution in Kotlin (1.3.71) (judge verdict: Accepted)

import java.io.BufferedReader
import java.util.*

fun main() = agc019b()

@OptIn(ExperimentalStdlibApi::class)
fun agc019b() = SimpleFastIOWithToken_agc019b().exec {
    val s = readString()
    val n = s.length.toLong()

    val duplicateCount = s.groupingBy { it }.eachCount().map { it.value.toLong() }
        .map { it * (it - 1) / 2 }.sum()

    val answer = 2L + (n * (n - 1) / 2 - 1) - duplicateCount

    println(answer)
}

// region kokokara template dayo (^o^)
@Suppress("unused", "HasPlatformType", "MemberVisibilityCanBePrivate", "ClassName")
private class SimpleFastIOWithToken_agc019b(private val separator: String = System.lineSeparator()) {
    private val br: BufferedReader = System.`in`.bufferedReader()
    private var st: StringTokenizer = StringTokenizer("")
    private val sb: StringBuilder = StringBuilder()
    private fun prepareNext() = run { if (!st.hasMoreTokens()) st = StringTokenizer(br.readLine()) }

    fun readString(): String = run { prepareNext() }.run { st.nextToken() }
    fun readStringList(size: Int): List<String> = List(size) { readString() }
    fun readInt(): Int = Integer.valueOf(readString())
    fun readIntList(size: Int): List<Int> = List(size) { readInt() }
    fun readLong(): Long = java.lang.Long.valueOf(readString())
    fun readLongList(size: Int): List<Long> = List(size) { readLong() }
    inline fun <reified T> readArray(size: Int, init: () -> T): Array<T> = Array(size) { init() }
    inline fun <T> readList(size: Int, init: () -> T): List<T> = List(size) { init() }

    fun println(): Unit = run { sb.append(separator) }
    fun print(any: Any): Unit = run { sb.append(any) }
    fun println(any: Any): Unit = run { sb.append(any.toString() + separator) }

    fun exec(action: SimpleFastIOWithToken_agc019b.() -> Unit) = run {
        Thread(null, { action() }, "(^o^)", 128 * 1024 * 1024).apply { start() }.join()
    }.run { kotlin.io.print(sb) }

    fun readLine(): Nothing = error("readLine is disabled.")
}
// endregion kokomade template dayo (^o^)