#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int n;
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    cin>>n;
    int x,y,a,b;
    cin>>a>>b;
    for(int i=1;i<n;i++)
        {
            cin>>x>>y;
            if(x!=a)
                a=-100;
            if(y!=b)
                b=-100;
            if(a==-100&&b==-100)
                {
                cout<<"NO";
                return 0;
            }
    }
    cout<<"YES";
    return 0;
}