#include<bits/stdc++.h>
using namespace std;
int main(){
	int n;
	cin>>n;
	int a[n],b[n];
	for(int i=0;i<n;i++)
		cin>>a[i]>>b[i];
	for(int i=1;i<n;i++){
		if(!(a[i]==a[i-1])||(b[i]==b[i-1])){
			cout<<"NO";
			return 0;
		}
}
	cout<<"YES";
	return 0;
}