#include<bits/stdc++.h>
using namespace std;
int z[703][703];
int work(string x)
{
	return (x[0]-'A'+1)*26+x[1]-'A'+1;
}
int main()
{
	int n;
	scanf("%d",&n);
	for(int i=1;i<=n;i++)
	{
		string x1,x2;
		cin>>x1>>x2;
		z[work(x1)]=work(x2);
	}
	int js=0;
	for(int i=1;i<=702;i++)
	{
		if(i==z[z[i]]&&i<z[i])
		{
			js++;
		}
	}
	cout<<js;
	return 0;
}

样例能过