#include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include <algorithm>

using namespace std;

int main(){
  int n; string s;
  cin >> n >> s;
  int ans = 0;
  for (int i = 0; i < n; i++) {
    for (int j = i + 1; j < n; j++) {
      for (int k = j + 1; k < n; k++) {
        for (int l = k + 1; l < n; l++) {
          for (int m = l + 1; m < n; m++) {
            if (s[i] != s[j] && s[i] == s[k] && s[i] != s[l] && s[i] != s[m] &&
                                s[j] != s[k] && s[j] != s[l] && s[j] != s[m] &&
                                                s[k] != s[l] && s[k] != s[m] &&
                                                                s[l] != s[m]) {
              ans ++;
            }
          }
        }
      }
    }
  }
  cout << ans << endl;
}