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

#include<stdio.h>
#include<string.h>
#define ll long long//不加wa5个点
#define For(i,a,b) for(register long long i=a;i<=b;i++)
using namespace std;
const int maxn=2e5+10;
char s[maxn];
ll ans,n;
int c[30];
signed main(){
	scanf("%s",s+1);
	n=strlen(s+1);
	ans=n*(n-1)/2;
	For(i,1,n){
		c[s[i]-'a']++;
	}
	For(i,0,26){
		ans-=1ll*c[i]*(c[i]-1)/2;
	}
	ans++;
	printf("%lld\n",ans);
}