#include <iostream>
#include <vector>
#include <utility>
#include <tuple>
#include <algorithm>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef unsigned long ul;
typedef __int128 lll;

template <typename T> inline T qAbs(const T &t) { return t >= 0 ? t : -t; }

int main() {
    int T, x, y, c;
    bool h = true, v = true;
    cin >> T;
    cin >> x >> y;
    while (--T) {
        cin >> c;
        if (c != x)
            v = false;
        cin >> c;
        if (c != y)
            h = false;
    }
    cout << ((h || v) ? "YES" : "NO") << endl;
    return 0;
}