#include <bits/stdc++.h>
using namespace std;
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define ll long long
#define ull unsigned long long
#define ld long double
#define vl vector<long long>
#define vvl vector<vector<long long>>
#define rbf(a, x) for (auto& a : x)
#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define rep2(i, s, n) for (ll i = (s); i < (ll)(n); i++)
#define drep(i, x) for (ll i = ((ll)(x)-1); i >= 0; i--)
#define pll pair<long long,long long>
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define vvc vector<vector<char>>
#define vc vector<char>
#define vvb vector<vector<bool>>
#define vb vector<bool>
#define Maxe(x) *max_element(all(x))
#define Mine(x) *min_element(all(x))
#define Size(x) ((ll)(x).size())
#define umap unordered_map
const long long INF = 1LL << 60;
const long double pi = 3.1415926535897932;
#define Fi first
#define Se second
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};

    template<typename Num>
        constexpr Num mypow(Num a, long long b) {
            if(b==0)return 1;
            if (a==0)return 0;
            Num x = 1;
              while (b > 0) {
                if(b & 1)x*=a;
                a*=a;
                b >>= 1;
              }
              return x;
        }

    template<class T> inline bool chmin(T& a, T b) {
        if (a > b) {
            a = b;
            return true;
        }
        return false;
    }
    template<class T> inline bool chmax(T& a, T b) {
        if (a < b) {
            a = b;
            return true;
        }
        return false;
    }

//lis,modpow,uf,modncr,soinsubunkai,yakusurekkyo
//mint,dijkstra,gyakugen

    signed main(){
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
        ll n;
        string s;
        cin>>n>>s;
        ll res=0;
        rep(i,n-1){
            if(s[i]=='#'&&s[i+1]=='.'){
                res++;
                s[i+1]='#';
            }
        }
        cout<<res<<endl;
    }