#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001LL

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