#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll,ll>;
#define fix(x) fixed << setprecision(x)
#define asc(x) x, vector<x>, greater<x>
#define rep(i, n) for(ll i = 0; i < n; i++)
#define all(x) (x).begin(),(x).end()
template<class T>bool chmin(T&a, const T&b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool chmax(T&a, const T&b){if(a<b){a=b;return 1;}return 0;}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n,ans = 1,cnt = 0;
    string s;
    cin >> n >> s;
    string t(n,'.');
    s = t+s;
    for(int i=2*n-2;i>=0;i--){
        if(s[i]=='#'){
            s[i] = '.';
            cnt++;
        }
        if(cnt && s[i+1]=='.'){
            s[i] = '#';
            cnt--;
            ans = 2*n-i;
        }
    }
    cout << ans << '\n';
    return 0;
}