#include <bits/stdc++.h>
using namespace std;
 
#ifdef _MSC_VER
#include <intrin.h>
#endif
 
using ll = long long;
using ld = long double;
using ull = unsigned long long;
using P = pair<ll, ll>;

#define endl "\n"

#define rep1(i, n) for (ll i = 0; i < (ll)(n); i++)
#define rep2(i, a, b) for (ll i = (ll)(a); i < (ll)(b); i++)
#define OVERLOAD_REP(_1, _2, _3, name, ...) name
#define rep(...) OVERLOAD_REP(__VA_ARGS__, rep2, rep1)(__VA_ARGS__)
#define rrep(i, n) for (ll i = (ll)(n) - 1; i >= 0; i--)
 
#define all(s) (s).begin(), (s).end()
#define fi first
#define se second

const ll mod = 998244353;
const ll inf = 4000000000000000000ll;
const ld eps = ld(0.00000000001);
static const long double pi = 3.141592653589793;

template<class T>void vcin(vector<T> &n){for(int i=0;i<int(n.size());i++) cin>>n[i];}
template<class T,class K>void vcin(vector<T> &n,vector<K> &m){for(int i=0;i<int(n.size());i++) cin>>n[i]>>m[i];}
template<class T>void vcout(vector<T> &n){for(int i=0;i<int(n.size());i++){cout<<n[i]<<" ";}cout<<endl;}
template<class T>void vcin(vector<vector<T>> &n){for(int i=0;i<int(n.size());i++){for(int j=0;j<int(n[i].size());j++){cin>>n[i][j];}}}
template<class T>void vcout(vector<vector<T>> &n){for(int i=0;i<int(n.size());i++){for(int j=0;j<int(n[i].size());j++){cout<<n[i][j]<<" ";}cout<<endl;}cout<<endl;}
void yes(bool a){cout<<(a?"yes":"no")<<endl;}
void YES(bool a){cout<<(a?"YES":"NO")<<endl;}
void Yes(bool a){cout<<(a?"Yes":"No")<<endl;}
void possible(bool a){ cout<<(a?"possible":"impossible")<<endl; }
void Possible(bool a){ cout<<(a?"Possible":"Impossible")<<endl; }
void POSSIBLE(bool a){ cout<<(a?"POSSIBLE":"IMPOSSIBLE")<<endl; }
template<class T,class F>void print(pair<T,F> a){cout<<a.fi<<" "<<a.se<<endl;}
 
template<class T>auto min(const T& a){ return *min_element(all(a)); }
template<class T>auto max(const T& a){ return *max_element(all(a)); }
template<class T,class U>bool chmax(T &a,const U b) { if (a<b) { a=b; return 1; } return 0;}
template<class T,class U>bool chmin(T &a,const U b) { if (b<a) { a=b; return 1; } return 0;}
template<class T> void ifmin(T t,T u){if(t>u){cout<<-1<<endl;}else{cout<<t<<endl;}}
template<class T> void ifmax(T t,T u){if(t>u){cout<<-1<<endl;}else{cout<<t<<endl;}}
 
template <class T> using V   = vector<T>;
template <class T> using VV  = V<V<T>>;
template <class T> using VVV = V<V<V<T>>>;

template <class T>
auto mvec(T val, ll n) { return V<T>(n, val); }
template <class T, class... Args>
auto mvec(T val, ll n, Args... args) {
    return V<decltype(mvec(val, args...))>(n, mvec(val, args...));
}
 
vector<ll> divisor(ll x){ vector<ll> ans; for(ll i = 1; i * i <= x; i++){ if(x % i == 0) {ans.push_back(i); if(i*i!=x){ ans.push_back(x / i);}}}sort(all(ans)); return ans; }
ll pop(ll x){return __builtin_popcountll(x);}
ll poplong(ll x){ll y=-1;while(x){x/=2;y++;}return y;}
 
void cincout(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  cout<< fixed << setprecision(15);
}
 
//============================================================================
// main
//============================================================================
int main(){
  cincout();
  ll n,ans,max=0;  cin >> n;
  string s; cin >> s;
  auto a=mvec(0LL,n);
  ll cur=-n;
  rep(i,n){
  	if(s[i]=='#') cur=i;
  	else a[i]=i-cur;
  }
  cur=2*n;
  rrep(i,n){
  	if(s[i]=='#') cur=i;
  	else chmin(a[i],cur-i);
  }
  rep(i,n){
  	if(max<a[i]){
  		max=a[i];
  		ans=i+1;
  	}
  }
  cout << ans;
  return 0;
}