#include <iostream>
#include <algorithm>
#include <functional>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <queue>
#include <ctime>
#include <cassert>
#include <complex>
#include <string>
#include <cstring>
#include <chrono>
#include <random>
#include <bitset>
#include <array>
#include<utility>
#include<stack>
#include <iomanip>
//#include<atcoder/all>
//using namespace atcoder;
using namespace std;
#define P pair<int,int>
#define Graph vector<vector<int>>
#define float long double
#define rep(i,a,b) for(int i=(a);i<(b);++i)
#define repi(itr,m) for(auto itr=(m).begin();itr!=(m).end();itr++)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define vi vector<int>
#define int long long
const int INF=1e18;
int dx[8]={0,1,0,-1,-1,-1,1,1};
int dy[8]={1,0,-1,0,-1,1,-1,1};
template<typename T> inline bool chmax(T &a, T b) { return ((a < b) ? (a = b, true) : (false));}
template<typename T> inline bool chmin(T &a, T b) { return ((a > b) ? (a = b, true) : (false));}
struct point{
  int x,y;
};
void yn(bool t){
  if(t)cout<<"Yes"<<endl;
  else cout<<"No"<<endl;
}

int solve(){
  int n;cin>>n;
  
  vector<vector<char>>s(n+1);
  rep(i,1,n+1){
    char c;cin>>c;
    vector<char>v={c};
    s[i]=v;
  }
  int ans=0;
  queue<pair<vector<char>,int>>q;
  
  rep(i,1,n+1){
    q.push({s[i],i});
  }
  while(!q.empty()){
    pair<vector<char> ,int>p=q.front();q.pop();
    vector<char> t=p.first;int idx=p.second;
    if(t.size()==5){
      set<P>st;
      rep(i,0,5)rep(j,i+1,5){
        if(t[i]==t[j])st.insert({i,j});
      }
      if(st.size()==1){
        ans+=st.count({0,2});
      }
    }
    else{
      rep(i,idx+1,n+1){
        vector<char>v=t;
        v.push_back(s[i][0]);
        q.push({v,i});
      }
    }
  }
  cout<<ans<<endl;
  
  
  assert(true);
  return 0;
}

signed main(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  solve();
}