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

int n;
string s;
int main(){
    cin >> n >> s;
    vector<vector<int>> suff(n+1, vector<int>(26, 0));
    for (int x = 0; x < 26; x++){
        suff[n][x] = 0;
    }
    for (int i = n-1; i >= 0; i--){
        for (int x = 0; x < 26; x++){
            suff[i][x] = suff[i+1][x];
        }
        suff[i][s[i]-'A']++;
    }
    
    vector<vector<ll>> dp(n+1, vector<ll>(26*26, 0LL));
    for (int a = 0; a < 26; a++){
        for (int b = 0; b < 26; b++){
            dp[n][a*26 + b] = 0;
        }
    }
    for (int i = n-1; i >= 0; i--){
        int l = s[i] - 'A';
        int after = n - (i+1);
        for (int a = 0; a < 26; a++){
            for (int b = 0; b < 26; b++){
                int idx = a * 26 + b;
                ll extra = 0;
                if(a != b && l != a && l != b){
                    int sum = after - suff[i+1][a] - suff[i+1][b];
                    extra = sum - suff[i+1][l];
                }
                dp[i][idx] = dp[i+1][idx] + extra;
            }
        }
    }
    vector<vector<vector<ll>>> pre(26, vector<vector<ll>>(26, vector<ll>(n+1, 0LL)));
    vector<int> cnt(26, 0);
    for (int i = 0; i < n; i++){
        for (int a = 0; a < 26; a++){
            for (int b = 0; b < 26; b++){
                pre[a][b][i+1] = pre[a][b][i];
            }
        }
        int ch = s[i] - 'A';
        for (int a = 0; a < 26; a++){
            pre[a][ch][i+1] += cnt[a];
        }
        cnt[ch]++;
    }
    
    ll ans = 0;
    for (int i3 = 2; i3 <= n-3; i3++){
        int a = s[i3] - 'A';
        for (int b = 0; b < 26; b++){
            if(b == a) continue;
            ans += dp[i3+1][a * 26 + b] * pre[a][b][i3];
        }
    }
    
    cout << ans << "\n";
}