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

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

    int count = 0;

    // 全ての i < j < k < l < m の組を探索
    for (int i = 0; i < N; ++i)
    for (int j = i + 1; j < N; ++j)
    for (int k = j + 1; k < N; ++k)
    for (int l = k + 1; l < N; ++l)
    for (int m = l + 1; m < N; ++m) {
        char c1 = S[i], c2 = S[j], c3 = S[k], c4 = S[l], c5 = S[m];
        // 条件1: c1 == c3
        if (c1 != c3) continue;
        // 条件2: c1, c2, c4, c5 はすべて異なる
        set<char> unique_letters = {c1, c2, c4, c5};
        if (unique_letters.size() == 4)
            count++;
    }

    cout << count << '\n';
    return 0;
}