#include <iostream>
#include<vector>
using namespace std;
int main(void){
    int n;
    string s;
    cin >> n;
    cin >> s;
   vector<int> b(n + 1);
   vector<int> w(n + 1);
   for(int i = 1;i <= n;i++){
         if(s[i - 1] == '#')b[i]++;
         else w[i]++;
         b[i] += b[i - 1];
         w[i] += w[i - 1];
   }
   int ans = n;
   for(int i = 0;i <= n;i++){
         ans = min(ans,b[i] + w[n] - w[i]);
   }
   cout << ans << endl;
}

