#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>
#define ll long long

using namespace std;


int main(){
    int n;
    cin >> n;
   // ll a[n];
    ll w,e;
    ll flag=0;
    cin>>w>>e;
    for(int a0 = 1; a0 < n; a0++){
        int x;
        int y;
       // cin >> a[a0]>>b[a0];
        cin>>x>>y;
        ll z=x;
        ll q=y;
        if(z==w||q==e)
            continue;
        else{
            flag=1;
        break;}
        
        }
    if (flag==1)
        cout<<"NO"<<endl;
    else
        cout<<"YES"<<endl;
    return 0;
}