#![allow(unused_imports,non_snake_case,dead_code)]
use std::{cmp::Reverse as Rev,collections::*,iter::*};
use proconio::{marker::*,*};


#[fastout]
fn main(){
    input!{
        n:usize,
        s:Chars,
    }

    let mut ans=0;
    for a in 0..n{
        for b in a+1..n{
            if s[a]==s[b]{
                continue;
            }
            for c in b+1..n{
                if s[a]!=s[c]{
                    continue;
                }
                for d in c+1..n{
                    if s[a]==s[d] || s[b]==s[d]{
                        continue;
                    }
                    for e in d+1..n{
                        if s[a]==s[e] || s[b]==s[e] || s[d]==s[e]{
                            continue;
                        }
                        ans+=1;
                    }
                }
            }
        }
    }
    println!("{ans}");
}