#include<bits/stdc++.h>
using namespace std;
#include <unordered_set>
#include <random>
//#define int long long
#define REP(i,m,n) for(int i=(m);i<(n);i++)
#define rep(i,n) REP(i,0,n)
#define pb push_back
#define all(a) a.begin(),a.end()
#define rall(c) (c).rbegin(),(c).rend()
#define mp make_pair
#define endl '\n'
//#define vec vector<ll>
//#define mat vector<vector<ll> >
#define fi first
#define se second
#define double long double
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll,ll> pll;
//typedef long double ld;
typedef complex<double> Complex;
const ll INF=1e9+7;
const ll MOD=998244353;
const ll inf=INF*INF;
const ll mod=MOD;
const ll inv2=499122177;
const ll MAX=200010;
const double PI=acos(-1.0);
typedef vector<vector<ll> > mat;
typedef vector<ll> vec;

ll dx[]={0,1,0,-1,-1,-1,1,1};
ll dy[]={1,0,-1,0,-1,1,-1,1};



void solve(){
    ll N;
    cin>>N;
    string S;
    cin>>S;
    ll la=N;
    ll z=0;
    ll ans=0;
    //何回待つか
    ll ma=0;

    for(int i=N-1;i>=0;i--){
        if(S[i]=='#'){
            if(la==N){
                la=i;
                ma=max(ma,N-i);
                continue;
            }
            z=max(0LL,(N-la)+2+z-(N-i));
            la=i;
            ma=max(ma,N-i);
        }
    }
    cout<<z+ma<<endl;
}

signed main(){
    //cin.tie(0);
    //ios::sync_with_stdio(false);
    solve();
}