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 Rust (1.15.1) (judge verdict: Accepted)

use std::io::*;
use std::str::FromStr;

fn main() {
    let s: Vec<char> = read::<String>().chars().collect();
    let n = s.len();
    /*
    let mut sum = 0;
    for i in 0..n {
        let mut l = i;
        let mut r = i;
        let mut cnt = 0;
        while 0 < l && r < n - 1 {
            l -= 1;
            r += 1;
            if s[l] == s[r] {
                cnt += 1;
            } else {
                break;
            }
        }
        sum += cnt;
        println!("{}:{}", i, cnt);
    }
    for i in 0..n-1 {
        let mut l = i;
        let mut r = i + 1;
        let mut cnt = 0;
        while r < n {
            if s[l] == s[r] {
                cnt += 1;
            } else {
                break;
            }
            if l == 0 {
                break;
            }
            l -= 1;
            r += 1;
        }
        sum += cnt;
        println!("{}:{}", i, cnt);
    }*/
    let mut vec: Vec<Vec<usize>> = vec![Vec::new(); 26];
    for i in 0..n {
        let j = s[i] as usize - 'a' as usize;
        vec[j].push(i);
    }

    let mut sum = 0;
    for i in 0..26 {
        if vec[i].is_empty() {
            continue;
        }
        let m = vec[i].len();
        sum += m * (m-1) / 2;
    }

    println!("{}", 1 + n * (n-1) / 2 - sum);
}

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.unwrap() as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().unwrap()
}