#include<iostream>
#include<algorithm>
#include<string>
#include<vector>
#include<bits/stdc++.h>
#include<cmath>
using namespace etsd;

int main(){
  int N;
  cin>>N;
  char S[N];
  for(int i=0; i<N; ++i) cin>>S[i];
  vector<int> A;
  if(S[0]=='.') A.push_back(0);
  int count=0;
  for(int i=N-1; i>=0; --i){
    count++;
    if(S[i]!=S[i+1]) A.push_back(count);
    count=0;
  }
  
  int mn=100000000;
  for(int i=0; i<(A.size()+1)/2; ++i){
    int count=0;
    for(int j=0; j<2*i; ++j){
      if(j%2==0) count += A[j]; 
    }
    for(int j=2*i; j<A.size(); ++j){
      if(j%2==1) count += A[j];
    }
    mn=min(mn,count);
    count=0;
  }
  
  cout<<mn<<endl;
}