#include<iostream>
#include<stdlib.h>
#include<vector>
#include<algorithm>
#include<stdio.h>
#include<string>
#include<map>
#include<math.h>
#include<iomanip>
#include<set>

#define rep(i,n) for(ll i = 0; i < (ll)n; i++)
#define swap(a,b) a^=b;b^=a;a^=b;
//#define for(i,a,b) for (ll i=(a);i<(ll)b; i++)
#define print(x) std::cout << x << std::endl;

using namespace std;

typedef long long ll;

template<class T, class U> std::string replace(std::string s, const T& target, const U& replacement, bool replace_first = 0, bool replace_empty = 0);
bool isContain(int value, int under, int top);
vector<int> range(int x);

int main(void) {
	//Program Start

	int N;
	string S;
	
	cin >> N;
	cin >> S;

	int W_Num = 0;
	int B_Num = 0;

	for (int i = 0; i < N; i++) 
		if (S[i] == '.') W_Num++;

	B_Num = N - W_Num;

	//printf("W:%d B:%d\n", W_Num, B_Num);

	//Black -> White
	int BtoW = B_Num;

	for (int i = N - 1; i >= 0; i--) {
		if (S[i] == '#') BtoW--;
		else break;
	}

	//White -> Black
	int WtoB = W_Num;
	
	for (int i = 0; i < N; i++) {
		if (S[i] == '.') WtoB--;
		else break;
	}

	
	cout << min(WtoB, BtoW) << endl;

ProgramEndPointLabel:;

	//Program End
	system("pause");

	return 0;
}


vector<int> range(int y) {
	vector<int> result(y);
	for (int i = 0; i < y; i++)
		result[i] = i;
	return result;
}

bool isContain(int value, int under, int top) {
	if (under <= value && value <= top) return true;
	return false;
}

template<class T, class U> std::string replace(std::string s, const T& target, const U& replacement, bool replace_first, bool replace_empty) {
	using S = std::string;
	using C = std::string::value_type;
	using N = std::string::size_type;
	struct {
		auto len(const S& s) { return s.size(); }
		auto len(const C* p) { return std::char_traits<C>::length(p); }
		auto len(const C  c) { return 1; }
		auto sub(S* s, const S& t, N pos, N len) { s->replace(pos, len, t); }
		auto sub(S* s, const C* t, N pos, N len) { s->replace(pos, len, t); }
		auto sub(S* s, const C  t, N pos, N len) { s->replace(pos, len, 1, t); }
		auto ins(S* s, const S& t, N pos) { s->insert(pos, t); }
		auto ins(S* s, const C* t, N pos) { s->insert(pos, t); }
		auto ins(S* s, const C  t, N pos) { s->insert(pos, 1, t); }
	} util;

	N target_length = util.len(target);
	N replacement_length = util.len(replacement);
	if (target_length == 0) {
		if (!replace_empty || replacement_length == 0) return s;
		N n = s.size() + replacement_length * (1 + s.size());
		s.reserve(!replace_first ? n : s.size() + replacement_length);
		for (N i = 0; i < n; i += 1 + replacement_length) {
			util.ins(&s, replacement, i);
			if (replace_first) break;
		}
		return s;
	}

	N pos = 0;
	while ((pos = s.find(target, pos)) != std::string::npos) {
		util.sub(&s, replacement, pos, target_length);
		if (replace_first) return s;
		pos += replacement_length;
	}
	return s;
}
