#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r) - 1;i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n; cin >> n;
	string s; cin >> s;
	int ans = 0;
	vector<char>c;
	auto check = [&]()->void {
		if (c[0] != c[2])return;
		set<char>st;
		rep(i, 5)st.insert(c[i]);
		if (st.size() == 4)ans++;
	};
	auto dfs = [&](auto &&self, int idx)->void {
		if (c.size() == 5) {
			check();
			return;
		}
		rep2(i, idx, n) {
			c.push_back(s[i]);
			self(self, i + 1);
			c.pop_back();
		}
	};
	dfs(dfs, 0);
	cout << ans << endl;
	return 0;
}