#include <bits/stdc++.h>
using namespace std;
long unsigned int combi(long unsigned int a) {
  if (a == 0 || a == 1) return 0;
  return ((a * (a - 1)) / 2);
}
int main() {
  int n = 0;
  cin >> n;
  char arr[n];
  int letras[26];
  char temp = 0;
  long unsigned int res = 0;
  for (int i = 0; i < 26; i++) {
    letras[i] = 0;
  }
  for (int i = 0; i < n; i++) {
    cin >> temp;
    cin.ignore(256, '\n');
    letras[temp - 97]++;
  }
  for (int i = 0; i < 26; i++) {
    res += (combi(letras[i] - (letras[i] / 2)) + (combi(letras[i] / 2)));
  }
  printf("%lu", res);
  return 0;
}
