#include<bits/stdc++.h>
using namespace std;
int n,ans;
string s;
int main()
{
	cin>>n>>s;
	for(int i=0;i<n-2;i++) 
		if(s[i]=='#'&&s[i+1]=='.'&&s[i+2]=='#')ans++;
	printf("%d",ans);
	return 0;
}