#include <bits/stdc++.h>

using namespace std;

long long n, x, y, a, b, s1, s2;

int main()
{
    cin >> n;
    cin >> a >> b;
    s1 = 0;
    s2 = 0;
    for (int i = 1; i < n; i++)
    {
        cin >> x >> y;
        if (x != a) s1 = 1;
        if (y != b) s2 = 1;
    }
    
    if (s1 * s2 == 0) cout << "YES";
    else cout << "NO";
    return 0;
}