#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <map>
#include <set>
#include <queue>
#include <iomanip>
#include <cstring>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i,n) for (int i = 0; i < int(n);i++)

int main(){
  int n;
  cin >> n;
  string s;
  cin >> s;
  vector<int> a(n);
  for (int i = n-1;i >= 0;i--){
    if (i == n-1){
      if (s[i] == '#') a[i] = 1;
      else a[i] = 0;
    }
    else if (s[i] == '#'){
      a[i] = a[i+1]+2;
    }
    else{
      a[i] = a[i+1];
    }
  }
  int ans = 0;
  for (int i = 0; i < n;i++){
    if (s[i] == '#'){
      ans = max(ans,a[i]);
    }
  }
  cout << ans << endl;

  return 0;
}