#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001



int main() {
	
	int n;
	cin>>n;
	string s;
	cin>>s;
	int ans = 0;
	vector<int> ii;
	rep(i,n){
		if(s[i]=='#')ii.push_back(i);
	}
	reverse(ii.begin(),ii.end());
	int last;
	rep(i,ii.size()){
		if(i==0){
			last = n-ii[i];
		}
		else{
			int t = n-ii[i];
			last = max(last+2,t);
		}
	}
	cout<<last<<endl;
	
    return 0;
}