#![allow(
    dead_code,
    non_snake_case,
    unused_imports,
    unused_mut,
    unused_variables,
    while_true,
    unused_assignments,
    clippy::needless_range_loop,
    clippy::ptr_arg,
    clippy::type_complexity,
    clippy::unnecessary_cast
)]
use proconio::{
    input,
    marker::{Chars, Usize1 as usize1},
};
use std::collections::{BinaryHeap, HashMap, HashSet, VecDeque};

fn main() {
    input! { N: usize, S: Chars };

    let mut ans = 0;
    for i0 in 0..N {
        for i1 in i0 + 1..N {
            for i2 in i1 + 1..N {
                for i3 in i2 + 1..N {
                    for i4 in i3 + 1..N {
                        let T = [S[i0], S[i1], S[i2], S[i3], S[i4]];
                        let cc = HashSet::<char>::from_iter(T.iter().cloned()).len();
                        if cc == 4 && T[0] == T[2] {
                            ans += 1;
                        }
                    }
                }
            }
        }
    }
    println!("{}", ans);
}