Osajono

input/code.cpp:10:34: error: '::main' must return 'int'
 long main(long argc, char* argv[]) {
                                  ^
input/code.cpp:10:6: warning: first argument of 'int main(long int, char**)' should be 'int' [-Wmain]
 long main(long argc, char* argv[]) {
      ^

#include <iostream>
#include <string>
#include <algorithm>

using std::cout;
using std::cin;
using std::string;
using std::count;

long main(long argc, char* argv[]) {
    // take input
    string input;
    cin >> input;

    // parse input
    long chars[26] = {0}; // A -> 0, B -> 1 ... Z -> 25
    for (int i = 0; i < 26; i++) {
        chars[i] = count(input.begin(), input.end(), (char)(i+65));
    }

    // do the actual things
    long sum = 0;

    for (int i = 0; i < 26; i++) {
        long p = 0;
        if (chars[i] % 2 == 0) {
            p = (chars[i] + 1) * (chars[i] / 2);
        } else {
            p = ((chars[i] + 1) * ((chars[i] - 1) / 2)) + ((chars[i] + 1) / 2);
        }
        sum += p;
    }

    // output
    cout << sum << "\n";
    return 0;
}