#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;
    int x,y,p,q,f=0;
    cin>>x>>y;
    p=x;q=y;
    for(int a0 = 0; a0 < n-1; a0++){
        
        cin >> x >> y;
        if(x==p ||y==q)
		{
			p=x;
			q=y;
		}
		else 
			f=1;
    }
    if(f==1)
		cout<<"NO"<<endl;
	else
		cout<<"YES"<<endl;
    return 0;
}