#include <bits/stdc++.h>
using namespace std;

struct init_ { init_(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(10); } } init_;

template<class C> auto operator>>(istream& in, C& c) -> typename enable_if<!is_void<decltype(c.begin())>::value && !is_same<C, string>::value, istream&>::type {
    for (auto& v : c) { in >> v; } return in; }
template<class C> auto operator<<(ostream& out, const C& c) -> typename enable_if<!is_void<decltype(c.begin())>::value && !is_same<C, string>::value, ostream&>::type {
    int i = 0; for (const auto& v : c) { if (i++) { out << ' '; } out << v; } return out; }
template<size_t N, class T, class R> using when_last = typename enable_if<N == tuple_size<remove_reference_t<T>>::value - 1, R>::type;
template<size_t N, class T, class R> using when_init = typename enable_if<N != tuple_size<remove_reference_t<T>>::value - 1, R>::type;
template<size_t N = 0, class T> auto operator>>(istream& in, T&& t) -> when_last<N, T, istream&> { return in >> get<N>(t); }
template<size_t N = 0, class T> auto operator>>(istream& in, T&& t) -> when_init<N, T, istream&> { return operator>><N + 1>(in >> get<N>(t), forward<T>(t)); }
template<size_t N = 0, class T> auto operator<<(ostream& out, const T& t) -> when_last<N, T, ostream&> { return out << get<N>(t); }
template<size_t N = 0, class T> auto operator<<(ostream& out, const T& t) -> when_init<N, T, ostream&> { return operator<<<N + 1>(out << get<N>(t) << ' ', t); }

#ifdef LOCAL
template<class T> void trace_(const char* s, const T& v) { cerr << s << "=" << v; }
template<class T, class... Ts> void trace_(const char* s, const T& v, const Ts&... vs) { for (; *s != ','; ++s) { cerr << *s; } cerr << "=" << v << ","; trace_(++s, vs...); }
#define TRACE(...) (cerr << "\033[2m\033[33m", trace_(#__VA_ARGS__, __VA_ARGS__), cerr << "\033[0m\n")
#else
#define TRACE(...)
#endif

int main() {
    int n;
    cin >> n;
    string s;
    cin >> s;
    int first_b = n;
    for (int i = 0; i < n; i++) {
        if (s[i] == '#') {
            first_b = i;
            break;
        }
    }
    int last_w = -1;
    for (int i = n-1; i >= 0; i--) {
        if (s[i] == '.') {
            last_w = i;
            break;
        }
    }
    TRACE(first_b, last_w);
    if (last_w < first_b) {
        cout << 0 << '\n';
        return 0;
    }
    int cntw = 0, cntb = 0;
    for (int i = first_b; i <= last_w; i++) {
        if (s[i] == '#') cntb++;
        else cntw++;
    }
    cout << min(cntw, cntb) << '\n';
}
