#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define For(a,b) for(ll i=a;i<b;i++)
#define For2(a,b) for(ll j=a;j<b;j++)
#define pb push_back

#define ll long long
#define mod 1000000007
using namespace std;


int main()
{
	int n,flag=1;
	cin>>n;
	int a[n],b[n];
	For(0,n)
		cin>>a[i]>>b[i];
    For(1,n)
    {
    	if(a[i-1]!=a[i])
    	{
    		flag=0;
    		break;
    	}
    }
    if(flag==0)
    {
    	flag=1;
    	For(1,n)
    {
    	if(b[i-1]!=b[i])
    	{
    		flag=0;
    		break;
    	}
    }
	}
    if(flag==1)
    	cout<<"YES"<<endl;
    else
    	cout<<"NO"<<endl;

    return 0;
}