#include<deque>
#include<queue>
#include<vector>
#include<algorithm>
#include<iostream>
#include<set>
#include<cmath>
#include<tuple>
#include<string>
#include<chrono>
#include<functional>
#include<iterator>
#include<random>
#include<unordered_set>
#include<unordered_map>
#include<array>
#include<map>
#include<bitset>
#include<iomanip>
using namespace std;
typedef long long int llint;
typedef long double lldo;
#define mp make_pair
#define mt make_tuple
#define pub push_back
#define puf push_front
#define pob pop_back
#define pof pop_front
#define fir first
#define sec second
#define res resize
#define ins insert
#define era erase
//ios::sync_with_stdio(false);
//std::cin.tie(0);
//<< setprecision(20)
//19234567892927;
const int mod=1e9+7;
const llint big=1e15+100;
const long double pai=3.141592653589793238462643383279502884197;
const long double ena=2.71828182845904523536;
const long double eps=1e-7;
template <class T,class U>void mineq(T& a,U b){if(a>b){a=b;}}
template <class T,class U>void maxeq(T& a,U b){if(a<b){a=b;}}
template <class T> void soun(T& ar){sort(ar.begin(),ar.end());ar.erase(unique(ar.begin(),ar.end()),ar.end());}
llint gcd(llint a,llint b){if(a%b==0){return b;}else return gcd(b,a%b);}
llint lcm(llint a,llint b){return a/gcd(a,b)*b;}
int solve(vector<bool> str,int n,int zan){//全部falseにする
	int hid=mod,mig=0,m=str.size(),now=n,ans=0;
	for(int i=0;i<m;i++){if(str[i]){if(hid==mod){hid=i;}mig=i;}}
	maxeq(mig,now);
	mineq(hid,now);
	while(now!=hid){
		now--;ans++;
		if(str[now]){zan--;str[now]=false;}
		else{zan++;str[now]=true;}
	}
	while(zan>0){
		if(str[now-1]){str[now-1]=false;zan--;now--;ans++;}
		else{
			if(str[now+1]){str[now+1]=false;zan--;}
			else{zan++;str[now+1]=true;}
			now++;ans++;
		}
	}
	return ans;
}
int main(void){
	int n,zan=0;cin>>n;
	string s;cin>>s;
	vector<bool>str(s.size()+2);
	for(int i=0;i<s.size();i++){
		if(s[i]=='#'){str[i+1]=true;zan++;}
	}
	int ans=solve(str,n,zan);
	n=str.size()-1-n;
	reverse(str.begin(),str.end());
	mineq(ans,solve(str,n,zan));
	if(ans==0){ans=3;}
	cout<<ans<<endl;
}