#include <bits/stdc++.h>
using namespace std;
template <class T1, class T2>
bool chmin(T1 &a, T2 b) {
  return b < a && (a = b, true);
}
template <class T1, class T2>
bool chmax(T1 &a, T2 b) {
  return a < b && (a = b, true);
}
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vll>;
using P = pair<ll, ll>;
using ld = long double;
using vld = vector<ld>;
using vi = vector<int>;
using vvi = vector<vi>;
vll conv(vi &v) {
  vll r(v.size());
  for (long long i = 0; i < (long long)(v.size()); i++) r[i] = v[i];
  return r;
}
inline void input(int &v) {
  v = 0;
  char c = 0;
  int p = 1;
  while (c < '0' || c > '9') {
    if (c == '-') p = -1;
    c = getchar();
  }
  while (c >= '0' && c <= '9') {
    v = (v << 3) + (v << 1) + c - '0';
    c = getchar();
  }
  v *= p;
}
template <typename T, typename U>
ostream &operator<<(ostream &o, const pair<T, U> &v) {
  o << "(" << v.first << ", " << v.second << ")";
  return o;
}
template <size_t...>
struct seq {};
template <size_t N, size_t... Is>
struct gen_seq : gen_seq<N - 1, N - 1, Is...> {};
template <size_t... Is>
struct gen_seq<0, Is...> : seq<Is...> {};
template <class Ch, class Tr, class Tuple, size_t... Is>
void print_tuple(basic_ostream<Ch, Tr> &os, Tuple const &t, seq<Is...>) {
  using s = int[];
  (void)s{0, (void(os << (Is == 0 ? "" : ", ") << get<Is>(t)), 0)...};
}
template <class Ch, class Tr, class... Args>
auto operator<<(basic_ostream<Ch, Tr> &os, tuple<Args...> const &t)
    -> basic_ostream<Ch, Tr> & {
  os << "(";
  print_tuple(os, t, gen_seq<sizeof...(Args)>());
  return os << ")";
}
ostream &operator<<(ostream &o, const vvll &v) {
  for (long long i = 0; i < (long long)(v.size()); i++) {
    for (long long j = 0; j < (long long)(v[i].size()); j++)
      o << v[i][j] << " ";
    o << endl;
  }
  return o;
}
template <typename T>
ostream &operator<<(ostream &o, const vector<T> &v) {
  o << '[';
  for (long long i = 0; i < (long long)(v.size()); i++)
    o << v[i] << (i != v.size() - 1 ? ", " : "");
  o << "]";
  return o;
}
template <typename T>
ostream &operator<<(ostream &o, const deque<T> &v) {
  o << '[';
  for (long long i = 0; i < (long long)(v.size()); i++)
    o << v[i] << (i != v.size() - 1 ? ", " : "");
  o << "]";
  return o;
}
template <typename T>
ostream &operator<<(ostream &o, const set<T> &m) {
  o << '[';
  for (auto it = m.begin(); it != m.end(); it++)
    o << *it << (next(it) != m.end() ? ", " : "");
  o << "]";
  return o;
}
template <typename T>
ostream &operator<<(ostream &o, const unordered_set<T> &m) {
  o << '[';
  for (auto it = m.begin(); it != m.end(); it++)
    o << *it << (next(it) != m.end() ? ", " : "");
  o << "]";
  return o;
}
template <typename T, typename U>
ostream &operator<<(ostream &o, const map<T, U> &m) {
  o << '[';
  for (auto it = m.begin(); it != m.end(); it++)
    o << *it << (next(it) != m.end() ? ", " : "");
  o << "]";
  return o;
}
template <typename T, typename U, typename V>
ostream &operator<<(ostream &o, const unordered_map<T, U, V> &m) {
  o << '[';
  for (auto it = m.begin(); it != m.end(); it++) o << *it;
  o << "]";
  return o;
}
vector<int> range(const int x, const int y) {
  vector<int> v(y - x + 1);
  iota(v.begin(), v.end(), x);
  return v;
}
template <typename T>
istream &operator>>(istream &i, vector<T> &o) {
  for (long long j = 0; j < (long long)(o.size()); j++) i >> o[j];
  return i;
}
template <typename T, typename S, typename U>
ostream &operator<<(ostream &o, const priority_queue<T, S, U> &v) {
  auto tmp = v;
  while (tmp.size()) {
    auto x = tmp.top();
    tmp.pop();
    o << x << " ";
  }
  return o;
}
template <typename T>
ostream &operator<<(ostream &o, const queue<T> &v) {
  auto tmp = v;
  while (tmp.size()) {
    auto x = tmp.front();
    tmp.pop();
    o << x << " ";
  }
  return o;
}
template <typename T>
ostream &operator<<(ostream &o, const stack<T> &v) {
  auto tmp = v;
  while (tmp.size()) {
    auto x = tmp.top();
    tmp.pop();
    o << x << " ";
  }
  return o;
}
template <typename T>
unordered_map<T, ll> counter(vector<T> vec) {
  unordered_map<T, ll> ret;
  for (auto &&x : vec) ret[x]++;
  return ret;
};
string substr(string s, P x) { return s.substr(x.first, x.second - x.first); }
void vizGraph(vvll &g, int mode = 0, string filename = "out.png") {
  ofstream ofs("./out.dot");
  ofs << "digraph graph_name {" << endl;
  set<P> memo;
  for (long long i = 0; i < (long long)(g.size()); i++)
    for (long long j = 0; j < (long long)(g[i].size()); j++) {
      if (mode && (memo.count(P(i, g[i][j])) || memo.count(P(g[i][j], i))))
        continue;
      memo.insert(P(i, g[i][j]));
      ofs << "    " << i << " -> " << g[i][j]
          << (mode ? " [arrowhead = none]" : "") << endl;
    }
  ofs << "}" << endl;
  ofs.close();
  system(((string) "dot -T png out.dot >" + filename).c_str());
}
size_t random_seed;
namespace std {
using argument_type = P;
template <>
struct hash<argument_type> {
  size_t operator()(argument_type const &x) const {
    size_t seed = random_seed;
    seed ^= hash<ll>{}(x.first);
    seed ^= (hash<ll>{}(x.second) << 1);
    return seed;
  }
};
};  // namespace std
int main() {
  int N;
  cin >> N;
  string S;
  cin >> S;
  ll ans = 0;
  for (int i = 0; i < N - 1; ++i) {
    if (S[i] == '#' && S[i + 1] == '.') ++ans;
  }
  cout << ans << endl;
}
