#include<bits/stdc++.h>
using namespace std;
using ll=long long;
using ld=long double;
const ll ILL=2167167167167167167;
const int INF=2100000000;
#define ALL(a)  (a).begin(),(a).end()
#define rep(i,a,b) for (int i=(int)(a);i<(int)(b);i++)
#define repr(i,a,b) for (int i=(int)(a);i>=(int)(b);i--)
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
template<class T> T vec_min(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmin(ans,x);return ans;}
template<class T> T vec_max(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmax(ans,x);return ans;}
template<class T> T vec_sum(vector<T> &a){T ans=T(0);for(auto &x:a) ans+=x;return ans;}
template<class T> void vec_out(vector<T> &a){for(auto &x:a) cout<<x<<" ";cout<<endl;}
template<class T> bool chmin(T &a,T b){if(b<a){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,T b){if(a<b){a=b;return 1;}else return 0;}


int main(void) {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  int n;
  string s;
  cin>>n>>s;
  int ans = 0;
  rep(i1, 0, n) rep(i2, i1+1, n) rep(i3, i2+1, n)
  rep(i4, i3+1, n) rep(i5, i4+1, n) {
    if (s[i1]==s[i3]
        && s[i1]!=s[i2] && s[i1]!=s[i4] && s[i1]!=s[i5]
        && s[i2]!=s[i3] && s[i2]!=s[i4] && s[i2]!=s[i5]
        && s[i3]!=s[i4] && s[i3]!=s[i5]
        && s[i4]!=s[i5]) {
      ans++;
    }
  }
  cout<<ans<<endl;
  return 0;
}