#include<bits/stdc++.h>
using namespace std;
long long n,ans;
string a,b,tmp;
map <string,string> mp;
int main(){
	cin>>n;
	for(int i = 1;i <= n;i++){
		cin>>a>>b;
		tmp = a.substr(0,2);
		//cout<<"\n"<<tmp<<"\n";
		mp[tmp] = b;
	}
	for(auto i : mp){
		if(i.first == mp[i.second]&&i.second == mp[i.first]) ans++;
	}
	cout<<ans/2<<"\n";
	return 0;
}