#include <bits/stdc++.h>
#include <atcoder/dsu>
using namespace std;

#define rep(i,a) for(int i=0;i<a;i++)
#define f(i,a,b) for(int i=a;i<=b;i++)
#define rf(i,a,b) for(int i=a;i>=b;i--)

using ll = long long;
using ld = long double;
using vi= vector<int>;
using vvi= vector<vi>;
using vs= vector<string>;
using pii= pair<int, int>;
using vpii= vector<pii>;
#define endl '\n'

int main(void){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
   int n;
   cin >> n;
   if(n < 5){
   	cout << 0 << endl;
   	return 0;
   }
   ll ans=0;
   string s;
   cin >> s;
   int moji1, moji2, moji3, moji4, moji5;
   rep(i,n-4){
   	moji1=s[i];
   	f(j,i+1,n-4){
   		if(s[i]==s[j])continue;
   		else{
   			moji2 = s[j];
   			f(k,j+1,n-3){
   				if(s[k]!=moji1)continue;
   				else{
   					moji3 = s[k];
   					f(l,k+1,n-2){
   						if(s[l]==moji1 || s[l] == moji2)continue;
   						else{
   							moji4=s[l];
   							f(m,l+1,n-1){
   								if(s[m]==moji1 || s[m] == moji2 || s[m] == moji4)continue;
   								else ans++;
   							}
   						}
   					}
   				}
   			}
   		}
   }
   }
   cout << ans << endl;
   
}