use std::collections::BTreeSet;

use proconio::{fastout, input, marker::Chars};

const DIRS: [(isize, isize); 4] = [(0, 1), (1, 0), (0, -1), (-1, 0)];

trait OrdExt {
    fn chmax(&mut self, other: Self) -> bool;
    fn chmin(&mut self, other: Self) -> bool;
}

impl<T: Ord> OrdExt for T {
    fn chmax(&mut self, other: Self) -> bool {
        if *self < other {
            *self = other;
            true
        } else {
            false
        }
    }

    fn chmin(&mut self, other: Self) -> bool {
        if *self > other {
            *self = other;
            true
        } else {
            false
        }
    }
}

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

    let mut ans = 0;

    for a in 0..n {
        for b in a + 1..n {
            for c in b + 1..n {
                for d in c + 1..n {
                    for e in d + 1..n {
                        let t = [s[a], s[b], s[c], s[d], s[e]];
                        if is_cpctf_like(t) {
                            ans += 1;
                        }
                    }
                }
            }
        }
    }

    println!("{}", ans);
}

fn is_cpctf_like(s: [char; 5]) -> bool {
    s[0] == s[2] && BTreeSet::from(s).len() == 4
}