#include <bits/stdc++.h>
#ifdef __DEBUG__
    #define DBG(X) cout << #X << " = " << (X) << endl;
    #define SAY(X) cout << (X) << endl;
#else
    #define DBG(X)
    #define SAY(X)
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

int dx[]={1, 0, -1, 0, 1,-1, 1,-1};
int dy[]={0, 1, 0, -1, 1, 1,-1,-1};
const int INT_INF = (int)(2e9);
const ll  LL_INF = (ll)(2e18);

inline void fast_io() { ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); };
template<typename T, typename S> inline ostream& operator<<(ostream& os, const pair<T, S> p) { cout << "[" << p.first << ";" << p.second << "]"; return os; }
template<typename T, typename S> inline ostream& operator<<(ostream& os, const map<T, S> p) { for (auto el : p) cout << "[" << el.first << ";" << el.second << "]"; return os; }
template<typename T> inline ostream& operator<<(ostream& os, const vector<T>& v) { for (auto el : v) cout << el << " "; return os; }
template<typename T> inline ostream& operator<<(ostream& os, const deque<T>& v) { for (auto el : v) cout << el << " "; return os; }
template<typename T> inline ostream& operator<<(ostream& os, const set<T>& v) { for (auto el : v) cout << el << " "; return os; }
template<typename T> inline vector<T> fetch_vec(int sz) { vector<T> ret(sz); for (auto& elem : ret) cin >> elem; return ret; }

int N;
string S;
void input(){
    fast_io();
    cin >> N >> S;
}

int solve(){
    string T = S;
    string V = S;
    // ll ans = 0;
    // for (int i = 0; i < N-1; i++)
    // {
    //     if(S[i]=='#' && S[i+1]=='.'){
    //         S[i+1]='#';
    //         ans++;
    //     }
    // }
    // ll ans_rev = 0;
    // for (int i = N-1; i > 0; i--)
    // {
    //     if(T[i-1]=='#' && T[i]=='.'){
    //         T[i-1]='.';
    //         ans_rev++;
    //     }
    // }

    int le = 0, ri = N-1;
    int ans = 0;
    while(ri-le>0){
        while(V[ri]=='#') ri--;
        while(V[le]=='.') le++;
        if(ri<=le) break;
        if(V[le]=='#' && V[ri]=='.'){
            int L=0,R=0;
            while(V[le+L]=='#') L++;
            while(V[ri-R]=='.') R++;
            if(L<R) {ans+=L;le+=L;}
            else {ans+=R;ri-=R;}
        }
    }
    cout << ans << endl;
    // DBG(S)
    // DBG(T)
    // cout << min(ans, ans_rev) << endl;    
    return 0;
}   

int main()
{
    input();
    solve();
    return 0;
}