use std::collections::HashSet;


fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).ok();
    let n: usize = n.trim().parse().unwrap();
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    let s = s.trim().chars().collect::<Vec<char>>();

    let mut patterns = HashSet::new();
    for i in 0..n-1 {
        if s[i] == 'A' && s[i+1] == 'A' {
            patterns.insert((i+1, i+2));
        } else if s[i] == 'A' {
            patterns.insert((i+1, 0));
        } else if s[i+1] == 'A' {
            patterns.insert((i+2, 0));
        } else {
            patterns.insert((0, 0));
        }
    }
    println!("{}", patterns.len());
}