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

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

    long long ans = 0;
    for (int i1 = 0; i1 < N; ++i1) {
        for (int i2 = i1 + 1; i2 < N; ++i2) {
            for (int i3 = i2 + 1; i3 < N; ++i3) {
                if (S[i1] != S[i3]) continue; // S1 = S3 でなければならない
                for (int i4 = i3 + 1; i4 < N; ++i4) {
                    for (int i5 = i4 + 1; i5 < N; ++i5) {
                        char c1 = S[i1], c2 = S[i2], c3 = S[i3], c4 = S[i4], c5 = S[i5];
                        // S1 == S3 already confirmed
                        // 他は全部異なる必要あり
                        if (c2 == c1 || c2 == c4 || c2 == c5) continue;
                        if (c4 == c1 || c4 == c5) continue;
                        if (c5 == c1) continue;
                        ans++;
                    }
                }
            }
        }
    }

    cout << ans << endl;
    return 0;
}