#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, c1 = 0, c2 = 0;
    cin >> n;
   /* for(int a0 = 0; a0 < n; a0++){
        int x;
        int y;
        cin >> x >> y;
    }*/
    
   int a[20],i;
    for(i= 0;i < 2*n; i++)
        {
            cin>> a[i];
        
        }
    for(i = 2;i < 2*n; i = i+2)
        {
       if(a[i]!= a[i-2])
           {
           c1++;
           break;
       }
    }
      for(i = 3;i < 2*n; i = i+2)
        {
       if(a[i]!= a[i-2])
           {
           c2++;
           break;
       } 
      }
          if(c1==0 || c2 == 0)
              cout<<"YES";
          else 
              cout<<"NO";
    return 0;
}