#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */  
    int n;
    cin >> n;
    int f = -1;
    int ans = 1;
    typedef pair<int,int>pii;
    pii a,b;
    cin >> a.first >> a.second >> b.first >> b.second;
    if(a.first == b.first) f = 1;
    else if(a.second == b.second) f = 2;
        
    if(f == -1) ans = 0;
    for(int i  = 0; i < n; i++) {
        cin >> a.first >> a.second;
        if(f==1 && a.first != b.first) ans = 0;
        if(f == 2 && a.second  != b.second) ans = 0;
    }
    if(ans) cout << "YES" << endl;
    else cout << "NO" << endl;
    return 0;
}