#include<bits/stdc++.h>
#include<atcoder/all>
using namespace atcoder;
//using mint = modint1000000007;
using mint = modint998244353;
//g++ -I/opt/ac-library ./**.cpp
using namespace std;
using ll = long long;
using ull = unsigned long long;
//const long long MOD = 1000000007;
const long long MOD = 998244353;
const long double PI = 3.14159265358979;
const long long INF = 1LL<<60;
template <typename T> bool chmax(T &a, const T& b){if(a < b){a = b;return true;}return false;}
template <typename T> bool chmin(T &a, const T& b){if(a > b){a = b;return true;}return false;}
#define deb(var) do{cout << #var << " : "; view(var);}while(0)
template<typename T> void view(T e){cout << e << endl;}
void view(vector<string>& v){cout << endl;for(auto& s :v){view(s);}cout << endl;}
template<typename T> void view(vector<T>& v){for(auto& e :v){cout << e << " ";}cout << endl;}
template<typename T> void view(vector<vector<T>>& vv){cout << endl;for(auto& v:vv){view(v);}}
ll gcd(ll a, ll b){if (b == 0) return a;else return gcd(b, a % b);}
ll lcm(ll x,ll y){return ll(x/gcd(x,y))*y;}
template<typename T> using min_priority_queue = priority_queue<T, vector<T>, greater<T>>;
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define int long long


int32_t main() {
    int n; cin >> n;
    string s; cin >> s;
    int d = -INF;
    for (int i=n-1; i>=0; i--) {
        if (s[i] == '#') {
            d = max(d + 2, n - i);
        }
    }
    cout << d << "\n";
}