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

int main() {
    int N;
    string S;
    cin >> N >> S;
    
    long long count = 0;
    
    for (int a = 0; a < N; a++) {
        for (int b = a + 1; b < N; b++) {
            for (int c = b + 1; c < N; c++) {
                for (int d = c + 1; d < N; d++) {
                    for (int e = d + 1; e < N; e++) {
                        char c1 = S[a];
                        char c2 = S[b];
                        char c3 = S[c];
                        char c4 = S[d];
                        char c5 = S[e];
                        
                        if (c1 == c3 && 
                            c1 != c2 && c1 != c4 && c1 != c5 && 
                            c2 != c3 && c2 != c4 && c2 != c5 && 
                            c3 != c4 && c3 != c5 && 
                            c4 != c5) {
                            count++;
                        }
                    }
                }
            }
        }
    }
    
    cout << count << endl;
    return 0;
}