#include <iostream>
#include <algorithm>
#include <math.h>
#include <string.h>
using namespace std;


int main(void)
{
    int N, A[20], B[20], flag = 1, c = 0;
    cin>>N;
    int a, b;
    cin>>A[0]>>B[0];
    cin>>A[1]>>B[1];
    if(A[0] == A[1])
    {
        a = A[0];
        c = 1;
    }
    else if(B[0] == B[1])
    {
        b = B[0];
        c = 2;
    }
    for(int i = 2; i < N; i++)
    {
        cin>>A[i]>>B[i];
        if(c == 1)
        {
            if(A[i] != a)
            {
                flag = 0;
            }
        }
        else if(c == 2)
        {
           if(B[i] != b)
           {
               flag = 0;
           }
        }
    }
    if(c == 0)
        flag = 0;
    if(flag == 1)
        cout<<"YES\n";
    else
        cout<<"NO\n";
    return 0;
}