#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <string>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <climits>
#include <cstring>
#include <cstdlib>
#include <fstream>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;


int main(){
    int n;
    cin >> n;
    vector<int> a;
    for(int a0 = 0; a0 < n; a0++)
    {
        int x;
        int y;
        cin >> x >> y;
        a.push_back(x);
        a.push_back(y);
    }
    int flag1 = 0;
    int flag2 = 0;
    for(int i = 0; i < a.size() - 2; i = i + 2)
    {
        if(a[i] != a[i+2])
        {
            flag1 = 1;
            break;
        }
    }
    
    for(int i = 1; i < a.size()-1; i = i + 2)
    {
        if(a[i] != a[i+2])
        {
            flag2 = 1;
            break;
        }
    }
    if(flag1 == 1 && flag2 == 1)
        cout << "NO";
    else
        cout << "YES";
    
    
    return 0;
}