#include "pch.h"
/////ここから下を提出///////////////////////////////////////////////////////////////
#include <iostream>
#include <vector>
#include <algorithm>
#include <fstream>
#include <string>
#include <math.h>
//#include <istream>
//#include <sstream>
using namespace std;

int main()
{
	int N;
	string S1;
	string S2;
	int f = 0;
	int ANS1 = 0;
	int ANS2 = 0;
	cin >> N;
	cin >> S1;
	S2 = S1;

	for (int i = 0; i < N; i++)
	{
		if (S1[i] == '#'&&S1[i+1]=='.')
		{
			S1[i + 1] = '#';
			ANS1++;
		}
	}

	for (int i = 0; i < N; i++)
	{
		if (S2[i] == '#'&&i!=N-1)
		{
			ANS2++;
		}
	}
	cout << min(ANS1,ANS2) << endl;
}
