#define _USE_MATH_DEFINES
#include<iostream>
#include<vector>
#include<algorithm>
#include<cmath>
#include<string>
#include<iomanip>
#include<numeric>
#include<queue>
#include<deque>
#include<stack>
#include<set>
#include<map>
#include<random>
#include<bitset>
#include<cassert>
#include<complex>
#include<fstream>
using namespace std;
int main(){
	int n;
	string s;
	cin>>n>>s;
	vector<int>ans;
	for(int i=n-1;i>=0;i--){
		if(s[i]=='#'){
			if(ans.empty())
				ans.push_back(n-i);
			else
				ans.push_back(max(n-i,ans.back()+2));
		}
	}
	cout<<ans.back()<<endl;
}