#pragma GCC optimize("Ofast") 
#include <bits/stdc++.h>
using namespace std;
using ll = long long int ;
using ld = long double ;
using P = pair<ll,ll>;
using Graph= vector<vector<ll>>;
struct edge{ll to ; ll cost ;} ;
using graph =vector<vector<edge>> ;
#define rep(i,n) for (ll i=0; i < (n); ++i)
#define rep2(i,n,m) for(ll i=n;i<=m;i++)
#define rep3(i,n,m) for(ll i=n;i>=m;i--)
#define pb push_back 
#define eb emplace_back 
#define ppb pop_back 
#define mpa make_pair 
#define fi first  
#define se second  
#define set20 cout<<fixed<<setprecision(20)  ;
const ll INF=1e18 ;   
inline void chmax(ll& a,ll b){a=max(a,b);}  
inline void chmin(ll& a,ll b){a=min(a,b);} 
long double pi=acos(-1) ;  
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 dx[4] {1,0,-1,0} ;
ll dy[4] {0,1,0,-1} ;
#define debug cout<<888<<endl ;


// ミント
//int mod ;  //任意modではconst外す
const ll mod = //1e9+7 ;//924844033;  
  998244353;


struct mint {
  ll x; // typedef long long ll;
  mint(ll x=0):x((x%mod+mod)%mod){}
  mint operator-() const { return mint(-x);}
  mint& operator+=(const mint a) {
    if ((x += a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator-=(const mint a) {
    if ((x += mod-a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator*=(const mint a) { (x *= a.x) %= mod; return *this;}
  mint operator+(const mint a) const { return mint(*this) += a;}
  mint operator-(const mint a) const { return mint(*this) -= a;}
  mint operator*(const mint a) const { return mint(*this) *= a;}
  mint pow(ll t) const {
    if (!t) return 1;
    mint a = pow(t>>1);
    a *= a;
    if (t&1) a *= *this;
    return a;
  }
  
  // for prime mod
  mint inv() const { return pow(mod-2);}
  mint& operator/=(const mint a) { return *this *= a.inv();}
  mint operator/(const mint a) const { return mint(*this) /= a;}
};
istream& operator>>(istream& is, const mint& a) { return is >> a.x;}
ostream& operator<<(ostream& os, const mint& a) { return os << a.x;}
//昆布
struct combination {
  vector<mint> fact, ifact;
  combination(int n):fact(n+1),ifact(n+1) {
    assert(n < mod); //任意modではここ消すcombmain内に
    fact[0] = 1;
    for (int i = 1; i <= n; ++i) fact[i] = fact[i-1]*i;
    ifact[n] = fact[n].inv();
    for (int i = n; i >= 1; --i) ifact[i-1] = ifact[i]*i;
  }
  mint operator()(int n, int k) {
    if (k < 0 || k > n) return 0;
    return fact[n]*ifact[k]*ifact[n-k];
  }
  mint p(int n,int k){
    return fact[n]*ifact[n-k] ; //kは個数
  }
  }  c(1000005);
 
 
mint modpow(ll a,ll b){
 if(b==0) return 1 ;
 mint c= modpow(a,b/2) ;
 if(b%2==1) return c*c*a ;
 else return c*c ;
}

mint mmodpow(mint a,ll b){
  if(b==0) return 1ll ;
  mint c=mmodpow(a,(b/2)) ;
  if(b%2==1) return c*c*a ;
  else return c*c ;
}
mint komb(ll n,ll m){
  mint x=1 ;mint y=1 ;
  rep(i,m){
    x*= n-i ;
    y*= i+1 ;
  }
  return x/y ;
}

 map<ll,ll> factor(ll n){  //素因数とオーダーをマップで管理
  map <ll,ll> ord ;  
  for(ll i=2;i*i<=n;i++){
        if(n%i==0){
            int res=0;
            while(n%i==0){
                n/=i;
                res++;
            }
            ord[i]=res;
        }
  }
  if(n!=1) ord[n]++;
  return ord ;
  }

struct UnionFind {
  vector<int> d;
  UnionFind(int n=0): d(n,-1) {}
  int find(int x) {
    if (d[x] < 0) return x;
    return d[x] = find(d[x]);
  }
  bool unite(int x, int y) {
    x = find(x); y = find(y);
    if (x == y) return false;
    if (d[x] > d[y]) swap(x,y);
    d[x] += d[y];
    d[y] = x;
    return true;
  }
  bool same(int x, int y) { return find(x) == find(y);}
  int size(int x) { return -d[find(x)];}
};

// sum(x) x以下の和
// sum(a,b) a以上b以下の和
template<typename T>
struct BIT {
  int n;
  vector<T> d;
  BIT(int n=0):n(n),d(n+1) {}
  void add(int i, T x=1) {  //x=1ならsumは個数のカウント
    for (i++; i <= n; i += i&-i) {
      d[i] += x;
    }
  }
  T sum(int i) {
    T x = 0;
    for (i++; i; i -= i&-i) {
      x += d[i];
    }
    return x;
  }
  T sum(int i,int j) {
    if(i>0) return sum(j)-sum(i-1);
    else return sum(j); } 
};



int main(){
  ios::sync_with_stdio(false) ;
  cin.tie(nullptr) ; 
  
  ll n; cin>>n;
  string s; cin>>s;
  ll now=-1;
  rep(i,n){
    if(s[n-1-i]=='#'){
      now+=2;
      chmax(now,(i+1));
    }
  }

  cout<<now<<endl;
  
  return 0;
}