#include "bits/stdc++.h"
using namespace std;

int main()
{
    long int T, flag = 1, points;
    cin>>T;
    vector <long int> Vec1, Vec2;
    for(int i = 0; i < T; i++)
    {
        long int A, B;
        cin >> A >> B;
        Vec1.push_back(A);
        Vec2.push_back(B);
    }

    points = Vec1[0];
    for(int i = 0; i < T; i++)
    {
        if(points != Vec1[i])
        {
            flag = 0;
            break;
        }
    }

    points = Vec2[0];


    if(flag == 0)
    {
        flag = 1;

        for(int i = 0; i < T; i++)
        {

            if(points != Vec2[i])
            {

                flag = 0;
                break;
            }
        }

    }

    (flag) ? cout << "YES" <<endl : cout << "NO" <<endl;

    return 0;
}