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

#define rep(i, a, b) for (int i = a; i < b; i++)
using ll = long long;

int main(){
    int N;
	string s;
    cin >> N >> s;
	map<char, int> mp;
	vector<map<char, int>> mpv(N);
	for(int i = N - 1; i >= 0; i--) {
		mp[s[i]]++;
		mpv[i] = mp;
	}
	vector<vector<int>> c(26);
	rep(i, 0, N) {
		int n = s[i] - 'A';
		c[n].push_back(i);
	}
	ll ans = 0;
	rep(i, 0, 26) {
		int sz = c[i].size();
		if(sz < 2) continue;
		char c2 = (char)(i + 'A');
		rep(j, 0, sz) {
			rep(k, j + 1, sz) {
				int l = c[i][j];
				int r = c[i][k];
				if(r - l < 2 || r + 1 >= N) continue;
				map<char, int> tmp = mpv[r + 1];
				using P = pair<char, int>;
				vector<P> p;
				for(auto it = tmp.begin(); it != tmp.end(); it++) {
					char f = it->first;
					if(f == c2) continue;
					p.push_back(P(f, it->second));
				}
				int sz = p.size();
				rep(m, l + 1, r) {
					if(s[m] == c2) continue;
					rep(n, 0, sz) {
						if(p[n].first == s[m]) continue;
						rep(o, n + 1, sz) {
							if(p[o].first == s[m]) continue;
							ans += p[n].second * p[o].second;
						}
					}
				}
			}
		}
	}
	cout << ans << endl;
}