#include<bits/stdc++.h>
#include<atcoder/all>
#define rep(i,n) for (int i = 0; i < int(n); ++i)
#define repp(i,n,m) for (int i = m; i < int(n); ++i)
#define repb(i,n) for (int i = int(n)-1; i >= 0; --i)
#define all(v) v.begin(),v.end()
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;
using P = pair<int, int>;
using PL = pair<long long, long long>;
using pdd = pair<long double, long double>;
using pil = pair<int,ll>;
using pli = pair<ll,int>;
using ppi = pair<P,int>;
using pip = pair<int,P>;
const int INF = 1001001007;
const long long mod1 = 1000000007LL;
const long long mod2 = 998244353LL;
const ll inf = 2e18;
const ld pi = 3.14159265358979323;
const ld eps = 1e-7;
template<typename T>void o(T a);
template<class T>istream &operator>>(istream &is,vector<T> &v){for(auto &e:v)is>>e;return is;}
template<class T>istream &operator>>(istream &is,vector<vector<T>> &v){for(auto &e:v)is>>e;return is;}
template<typename T>bool range(T a,T b,T x){return (a<=x&&x<b);}
template<typename T>bool rrange(T a,T b,T c,T d,T x,T y){return (range(a,c,x)&&range(b,d,y));}
template<typename T>void rev(vector<T> &v){reverse(v.begin(),v.end());}
void revs(string &s) {reverse(s.begin(),s.end());}
template<typename T>void sor(vector<T> &v, int f=0){sort(v.begin(),v.end());if(f!=0) rev(v);}
template<typename T>bool chmin(T &a,const T &b){if(a>b){a=b;return true;}return false;}
template<typename T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<typename T>void uniq(vector<T> &v){sor(v);v.erase(unique(v.begin(),v.end()),v.end());}
template<typename T>T cel(T a,T b){return (a+b-1)/b;}
template<typename T1, typename T2>void print(pair<T1,T2> a);
template<typename T>void print(vector<T> v);
template<typename T>void print(vector<vector<T>> v);
void print(){ putchar(' '); }
void print(bool a){ printf("%d", a); }
void print(int a){ printf("%d", a); }
void print(long a){ printf("%ld", a); }
void print(long long a){ printf("%lld", a); }
void print(char a){ printf("%c", a); }
void print(char a[]){ printf("%s", a); }
void print(const char a[]){ printf("%s", a); }
void print(long double a){ printf("%.15Lf", a); }
void print(const string& a){ for(auto&& i : a) print(i); }
template<class T> void print(const T& a){ cout << a; }
int out(){ putchar('\n'); return 0; }
template<class T> int out(const T& t){ print(t); putchar('\n'); return 0; }
template<class Head, class... Tail> int out(const Head& head, const Tail&... tail){ print(head); putchar(' '); out(tail...); return 0; }
void o(){cout<<"!?"<<endl;}
template<typename T>void o(T a){cout<<a<<endl;}
template<typename T1,typename T2>void print(pair<T1,T2> a){print(a.first);print(),print(a.second);}
template<typename T>void print(vector<T> v){for(auto ite=v.begin();ite!=v.end();){print(*ite);if(++ite!=v.end())print();}}
template<typename T>void print(vector<vector<T>> v){for(auto ite=v.begin();ite!=v.end();){print(*ite);if(++ite!=v.end())out();}}
void yes(){out("Yes");}
void no (){out("No");}
void yn (bool t){if(t)yes();else no();}
template<typename T>void dame(bool t, T s){if(!t){out(s);exit(0);}}
vector<int> dx = {0,1,0,-1,1,1,-1,-1};
vector<int> dy = {1,0,-1,0,1,-1,-1,1};
const string ALP = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const string alp = "abcdefghijklmnopqrstuvwxyz";
const string NUM = "0123456789";

ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
ll lcm(ll a,ll b){return a/gcd(a,b)*b;}
ll mpow(ll x,ll n,ll m){if(n==0)return 1LL;x%=m;ll a=mpow(x,n/2,m);a=a*a%m;return (n&1)?a*x%m:a;}

void solve(){
    int n; cin >> n;
    string s; cin >> s;
    int a = 0;
    int ans = 0;
    repb(i,n-1){
        if (s[i] == '#'){
            if (s[i+1] == '#') ans++;
        }
        else {
            ans--;
            if (ans < 0) ans = 0;
        }
        chmax(a,ans);
    }
    out(a);
}

int main(){
    int t = 1; //cin >> t;
    while(t--) solve();
}