#include <iostream>
#include <string>
using namespace std;

int main() {
	int count = 0;
	int n;
	string s;
	cin >> n >> s;
    if (n < 5) {
    	cout << 0 << endl;
        return 0;
    }
    for (int i = 0; i <= n - 5; ++i)
    for (int j = i + 1; j <= n - 4; ++j)
    for (int k = j + 1; k <= n - 3; ++k)
    for (int l = k + 1; l <= n - 2; ++l)
    for (int m = l + 1; m <= n - 1; ++m) {
    	if(s[i] == s[k] && s[j]!=s[k] && s[j]!=s[l] && s[j]!=s[m] && s[k]!=s[l] && s[k]!=s[m] && s[l]!=s[m]){
    		count++;
    	}
    }
	cout << count << endl;
    return 0;
}