#include<iostream>

using namespace std;

int main()
{
    unsigned short int n,x,y,tempx,tempy,flagx=0,flagy=0;
    cin>>n;
    cin>>tempx>>tempy;
    n--;
    while(n--)
    {
        cin>>x>>y;
        
        if(flagx==0 && x!=tempx)
            {
            flagx=1;
        }
        if(flagy==0 && y!=tempy)
            {
            flagy=1;
        }
        if(flagx==1 && flagy==1)
            {
            cout<<"NO";
            return 0;
        }
        
    }
    cout<<"YES";
    
}