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 mut s = s.trim().chars().collect::<Vec<char>>();

    s.reverse();
    let mut maxval = 0usize;
    let mut delay = 0usize;
    for i in 0..n {
        if s[i] == '.' {
            if delay > 0 { delay -= 1; }
            continue;
        }
        maxval = maxval.max(i+1+delay);
        delay += 1;
    }
    println!("{}", maxval);
}