#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;
    vector<int> v1,v2;
    cin >> n;
    for(int a0 = 0; a0 < n; a0++){
        int x;
        int y;
        cin >> x >> y;
        v1.push_back(x);
        v2.push_back(y);
    }
    int a = v1[0];
    int count=0;
    for(int i=1;i<v1.size();i++)
    {
       if(a!=v1[i]) 
        {  int b = v2[0];
           for(int j=1;j<v1.size();j++)
             {
               if(b!=v2[j])
               {
               count++;
                       }
           }
         
       }
    }
    if(count==0)
        cout<<"YES";
    else
        cout<<"NO";
    return 0;
}