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

int main(){
    // 入力の受け取り
    int n;
    cin >> n;
    string s;
    cin >> s;
    
    int ans = 0;
    
    for(int i = 0; i < (1 << n); i++){
        if (__builtin_popcount(i) != 5) continue;
        string str = "";
        for(int j = 0; j < n; j++){
            if((i >> j) & 1) str += s[j];
        }
        
        if(str[0] == str[1]) continue;
        if(str[0] != str[2]) continue;
        if(str[0] == str[3]) continue;
        if(str[0] == str[4]) continue;
        if(str[1] == str[3]) continue;
        if(str[1] == str[4]) continue;
        if(str[3] == str[4]) continue;

        ans++;
    }

    cout << ans << endl;
}