Osajono

#include <iostream>
#include <string>

int main()
{
	std::string input;
	std::cin >> input;

	unsigned long long output = 0;
	unsigned long characterCounts[ 26 ];

	for ( int i = 0; i < 26; ++i )
	{
		characterCounts[i] = 0;
	}

	for ( unsigned long i = 0; i < input.length(); ++i )
	{
		characterCounts[ input[ i ] - 'A' ]++;
	}

	for ( unsigned int i = 0; i < 26; ++i )
	{
		unsigned long count = characterCounts[ i ];
		output += ( count * (count + 1) ) / 2;
	}

	std::cout << output << "\n";

	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: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED