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 - 2) {
        if cs1[i] == '#' && cs1[i + 1] == '.' {
            if cs1[i + 2] == '.' {
                cs1[i] = '.';
                ans1 += 1;
            } else {
                cs1[i + 1] = '#';
                ans1 += 1;
            }
        }
    }

    if cs1[n - 2] == '#' && cs1[n  - 1] == '.' {
        ans1 += 1;
    }


    let mut ans2 = 0;
    let mut cs2 = cs.clone();
    cs2.reverse();
    for i in 0..(n - 2) {
        if cs2[i] == '.' && cs2[i + 1] == '#' {
            if cs2[i + 2] == '#' {
                cs2[i] = '#';
                ans2 += 1;
            } else {
                cs2[i + 1] = '.';
                ans2 += 1;
            }
        }
    }

    if cs2[n - 2] == '.' && cs2[n  - 1] == '#' {
        ans2 += 1;
    }

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