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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <map>
#include <unordered_map>
#include <set>
#include <climits>
using namespace std;
 
int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    string A;
    cin >> A;
    long long N = A.size();
    map<char, long long> mp;
    for(int i=0; i<26; i++) mp['a'+i] = 0;
    for(int i=0; i<N; i++) mp[A[i]]++;
 
    long long ans = (N*(N-1))/2;
    for(int i=0; i<26; i++){
        long long tmp = mp['a'+i];
        if(tmp <= 1) continue;
        ans -= (tmp*(tmp-1))/2;
    }
    ans++;
    cout << ans << endl;
 
    return 0;
}