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


int main() {
    unsigned n;
    cin >> n;
    bool vertical = false;
    bool horizontal = false;
    pair<int, int> last = make_pair(INT_MAX, INT_MAX);
    bool flag = false;
    for (auto i = 0; i < n; ++i) {
        int xi, yi;
        cin >> xi >> yi;
        if (last.first == INT_MAX && last.second == INT_MAX) {
            last.first = xi;
            last.second = yi;
        } else if (last.first == xi) {
            if (horizontal) {
                cout << "NO\n";
                flag = true;
                break;
            }
            vertical = true;
        } else if (last.second == yi) {
            if (vertical) {
                cout << "NO\n";
                flag = true;
                break;
            }
            horizontal = true;
        } else {
            cout << "NO\n";
            flag = true;
            break;
        }
    }
    if (flag == false) cout << "YES\n";
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}