import java.util.ArrayDeque;
import java.util.Arrays;
import java.util.Scanner;

class Main {

	void run() {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		String S = sc.next();
		boolean[] a = new boolean[S.length()];
		for (int i = 0; i < S.length(); ++i) {
			a[i] = S.charAt(i) == '.';
		}
		int ans = solve(Arrays.copyOf(a, a.length), n);
		{
			int s = 0;
			int t = a.length - 1;
			while (s < t) {
				boolean tmp = a[s];
				a[s] = a[t];
				a[t] = tmp;
				++s;
				--t;
			}
			n = S.length() - n + 1;
		}
		ans = Math.min(ans, solve(a, n));
		System.out.println(ans);
	}

	ArrayDeque<Integer> dq = new ArrayDeque<>();

	int solve(boolean[] a, int n) {
		int ret = Integer.MAX_VALUE / 3;
		int t = a.length - 1;
		int s = 0;
		while (a[t])
			--t;
		while (a[s])
			++s;
		if (t < n - 1)
			return ret;
		int cur = 0;
		for (int i = 0; i < a.length; ++i) {
			//s->t
			if (s < i && i <= t) {
				a[i] = !a[i];
				++cur;
			}
			if ((s <= i && i < n - 1) || (n - 1 < i && i <= s)) {
				a[i] = !a[i];
				++cur;
			}
		}
		for (int i = 0; i < a.length; ++i) {
			if (!a[i])
				dq.addLast(i);
		}
		while (!dq.isEmpty()) {
			if (dq.size() >= 2) {
				int u = dq.pollFirst();
				int v = dq.pollFirst();
				cur += (v - u) * 2;
			} else {
				int u = dq.pollFirst();
				cur += Math.abs((t - 1) - u) * 2 + 1;
			}
		}
		ret = Math.min(ret, cur);
		return ret;
	}

	void tr(Object... objects) {
		System.out.println(Arrays.deepToString(objects));
	}

	public static void main(String[] args) {
		new Main().run();
	}

}