#include<bits/stdc++.h>
using namespace std;

int main(){
	int n;
	cin>>n;
	string b[n+1],c[n+1],d[n+1],e[n+1];
	for(int i=0;i<n;i++){
		cin>>b[i]>>c[i]>>d[i]>>e[i];
	}
	int k[n+1],jie[n+1]; 
	for(int i=0;i<n;i++){
		for(int j=i+1;j<n;j++){
			if(b[i]==b[j])k[i]++;
			if(b[i]==e[j])jie[i]++;
		}
	}
	int AB=0,CD=0;
	for(int i=0;i<n;i++){
		if(k[i]>=2&&jie[i]>=1)AB++;
		if(k[i]>=1&&jie[i]>=2)CD++;
	}
	cout<<ceil(min(AB,CD)/2);
	return 0;
}