#include<bits/stdc++.h>
//#pragma GCC target("avx2")
//#pragma GCC optimize("O3")
//#pragma GCC optimize("unroll-loops")
using namespace std;
using ll=long long;
using ld=long double;
using ull=unsigned long long;
using i128 = __int128_t;
#define rep(i,n) for(ll i=0;i<ll(n);i++)
#define rep2(i,n) for(ll i=n-1;i>=0;i--)
#define rep3(i,a,b) for(ll i=a;i<=ll(b);i++)
#define rep4(i,a,b) for(ll i=a;i>=ll(b);i--)
#define forv(i,V) for(const auto& i:V)
#define all(x) x.begin(),x.end()
#define fi first
#define se second
#define SIZE(x) int(x.size())
//constexpr ll mod=998244353;
//constexpr ll mod=1000000007;
#define pi 3.14159265358979323
#define INF32 2147483647
#define INF64 9223372036854775807
#define faster ios::sync_with_stdio(false);std::cin.tie(nullptr)
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define rev reverse
#define vi vector<int>
#define vll vector<ll>
#define vpi vector<pair<int,int>>
#define vpll vector<pair<ll,ll>>
#define vvi vector<vector<int>>
#define vvll vector<vector<ll>>
#define prq priority_queue
#define lb lower_bound
#define ub upper_bound
const string YESNO[2] = {"NO", "YES"};
const string YesNo[2] = {"No", "Yes"};
const string yesno[2] = {"no", "yes"};
#define rall(n) (n).rbegin(),(n).rend()
#define INT(...) int __VA_ARGS__;scan(__VA_ARGS__)
#define LL(...) ll __VA_ARGS__;scan(__VA_ARGS__)
#define STR(...) string __VA_ARGS__;scan(__VA_ARGS__)
#define CHR(...) char __VA_ARGS__;scan(__VA_ARGS__)
#define DBL(...) double __VA_ARGS__;scan(__VA_ARGS__)
#define LD(...) ld __VA_ARGS__;scan(__VA_ARGS__)
template<typename T,typename U>
ostream &operator<<(ostream&os,const pair<T,U>&p){os<<p.first<<" "<<p.second;return os;}
template<typename T,typename U>
istream &operator>>(istream&is,pair<T,U>&p){is>>p.first>>p.second;return is;}
template<typename T>
ostream &operator<<(ostream&os,const vector<T>&v){for(auto it=v.begin();it!=v.end();){os<<*it<<((++it)!=v.end()?" ":"");}return os;}
template<typename T>
istream &operator>>(istream&is,vector<T>&v){for(T &in:v){is>>in;}return is;}
void scan(){}
template<class Head,class... Tail>
void scan(Head&head,Tail&... tail){cin>>head;scan(tail...);}
template<class T>
void print(const T &t){cout<<t<<'\n';}
template<class Head, class... Tail>
void print(const Head &head, const Tail &... tail){cout<<head<<' ';print(tail...);}
template<class... T>
void fin(const T &... a){print(a...);exit(0);}
ll max(int a,ll b){return max((ll)a,b);}
ll max(ll a,int b){return max((ll)b,a);}
ll min(int a,ll b){return min((ll)a,b);}
ll min(ll a,int b){return min((ll)b,a);}
//a以上b以下の個数
template<typename T>
ll RangeOK(ll a,ll b,vector<T> &v){
  return max(ub(all(v),b)-lb(all(v),a),0);
}
//setprecision(20)
int main(){
	LL(n);
	STR(s);
	ll now=0;
	ll ans=0;
	rep4(i,n-1,0){
		if(s[i]=='#'){
			ans=max(ans,now+n-i);
			now++;
		}
		else{
			now--;
			now=max(now,0);
		}
	}
	fin(ans);
}