Osajono

import java.util.ArrayList;

public class Main {
    public static void main(String[] args) {
        IO io = new IO();
        String input = io.next();
        long counter = 0;
        ArrayList<Long> amount = new ArrayList<>();
        ArrayList<Character> cha = new ArrayList<>();
        Character[] chars = { 'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z' };
        for (char c : chars) {
            cha.add(c);
            amount.add((long)0);
        }
        for (char c : chars) {
            for (int i = 0; i < input.length(); i++) {
                if (input.charAt(i)==c) {
                    amount.set(cha.indexOf(c),amount.get(cha.indexOf(c))+1);
                }
            }
        }

        for (int i = 0; i < cha.size(); i++) {
            long a = 1;
            long b = 0;
            for (int j = 0; j < amount.get(i); j++) {
                b += a;
                a++;
            }
            counter+=b;
        }

        io.println(counter);
        io.close();
    }
}


/*
public class Main {

    public static void main(String[] args) {

        IO io = new IO();
        String input = io.next();
        int counter = 0;

        char[] chars = input.toCharArray();
        int l = chars.length;

        for(int first=0; first < l; first++) {
            for (int second = first+1; second < l; second++) {
                if (chars[first]==chars[second]) {
                    counter++;
                }
            }
        }
        io.println(counter+l);
        io.close();
    }
} */

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED