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*/


#include<bits/stdc++.h>

using namespace std;
using lnln = long long;
using veci = vector<int>; //二次元はvector<veci>で我慢
using vecl = vector<long long>;
using vecs = vector<string>;
using vecb = vector<bool>;

#define repe(i,n) for(int i = 0; i < (n); ++i)    //ただのfor
#define eper(i,n) for(int i = (n)-1; i >= 0; --i) //逆からfor

#define been(a) a.begin(),a.end()   //sort(been(A))とかできる
#define neeb(a) a.rbegin(),a.rend() //逆からそれ

#define chax(a,b) a = max(a,b) //answの更新とかに
#define chin(a,b) a = min(a,b) //上に同じく

#define outY cout << "Yes\n" //出力さぼれて嬉しい(要セミコロン)
#define outN cout << "No\n"	 //上に
#define outM cout << "-1\n"	 //上に
#define outA(n) cout << (n) << "\n" //上のやつの汎用化した

int yonx[] = {0,1,0,-1}, yony[] = {-1,0,1,0}; //12時から時計回り四近傍
int hatx[] = {0,1,1,1,0,-1,-1,-1}, haty[] = {-1,-1,0,1,1,1,0,-1}; //八近傍

#ifdef __LOCAL //dbgn() -> 改行区切り
#define dbgn(N) cout << (N) << "\n";
#else
#define dbgn(N);
#endif

#ifdef __LOCAL //dbgs() -> 空白区切り
#define dbgs(N) cout << (N) << " ";
#else
#define dbgs(N);
#endif


int main(void)
{
	int N;
	string S;
	cin >> N >> S;


	map<char,int> exis;
	repe(i,N){
		exis[S[i]]++;
	}

	vector<string> cand;
	repe(i,N){
		if(2 <= exis[S[i]] and i < N-2){
			for(int n = i+1;n < N;n++){
				if(S[n] == S[i] and n < N-2){
					int star = i+1, fini = n;
					if(0 < fini-star){
						for(int t = star;t < fini;t++){
							for(int e = fini+1;e < N-1;e++){
								for(int g = e+1;g < N;g++){
									string kouh = "";
									kouh += S[i];    
									kouh += S[t];    
									kouh += S[n];    
									kouh += S[e];    
									kouh += S[g];    
									cand.push_back(kouh);
								}
							}
						}
					}
				}
			}
		}	
	}

	lnln answ = 0;
	repe(i,cand.size()){
		set<char> dupl;	
		repe(n,5) dupl.insert(cand[i][n]);

		if(dupl.size() == 4) answ++;
	}


	outA(answ);


	return 0;
}