#include<iostream>
#define F first
#define S second
using namespace std;
int main()
{
    int n,flag=0;
    pair<int,int> p,q;
    cin>>n;
    cin>>p.F>>p.S;
    for(int i=1;i<n;i++)
    {
        cin>>q.F>>q.S;
        if(p.F!=q.F && p.S!=q.S)
        {
            flag=1;
            break;
        }
    }
    if(flag==1)
        cout<<"NO"<<endl;
    else
        cout<<"YES"<<endl;
}