#include<bits/stdc++.h>
using namespace std;
using ll=long long;
int main(){
  ll N;
  cin>>N;
  string s;
  cin>>s;
  vector<ll>a(N,0);
  for(ll i=0;i<N-1;i++){
    if(s.at(i)=='#'&&s.at(i+1)=='.')a[i]=1;
  }
  vector<ll>S(N+1,0);
  for(ll i=0;i<N;i++)S[i+1]=S[i]+a[i];
cout<<S(N)<<endl;
}









