use std::iter::*;
use std::cmp::*;

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn print<T: std::fmt::Display>(x: T) -> () {
    println!("{}", x);
}


fn main() {
    let n: usize = read();
    let s: String = read();
    let cs: Vec<char> = s.chars().collect();

    let mut cs1 = cs.clone();
    let mut ans1 = 0;
    for i in 0..(n - 1) {
        if cs1[i] == '#' && cs1[i + 1] == '.' {
            cs1[i + 1] = '#';
            ans1 += 1;
        }
    }
    
    let mut ans2 = 0;
    let mut cs2 = cs.clone();
    cs2.reverse();
    for i in 0..(n - 1) {
        if cs2[i] == '#' && cs2[i + 1] == '.' {
            cs2[i + 1] = '.';
            ans2 += 1;
        }
    }

    let ans: usize = min(ans1, ans2);
    print(ans);
}
