Osajono

#include <iostream>

using namespace std;

long long chars[] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
bool hasValidData = true;
long long output=0;

int main() {
	while (hasValidData) {
		char in = ' ';
		cin >> in;
		int i = (int)in - (int)'A';
		if (i <= 27 && i >= 0) {
			chars[i]++;
		}
		else {
			hasValidData = false;
		}
	}
	for (int k = 0; k <= 27; k++)
	{
		int A = chars[k];
		if ((A / 2) * 2 == A) {
			output += (A + 1)*(A / 2);
		}
		else {
			output += A*((A / 2) + 1);
		}
	}
	cout << output;
	return 0;
}

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: WRONG ANSWER

Test 14

Group: 3

Verdict: WRONG ANSWER

Test 15

Group: 3

Verdict: WRONG ANSWER