#include <bits/stdc++.h>

using namespace std;


int main(){
    int n,lx,ly,x,y;
    cin >> n;
    for(int i = 0; i < n; i++){
        cin >> x >> y;
        if(i&&x!=lx&&y!=ly){
            cout<<"NO";
            return 0;
        }
        if(i&&x==lx&&y!=ly){
            y=100;
        }
        else if(i&&x!=lx&&y==ly){
            x=100;
        }
        lx=x;
        ly=y;
    }
    cout<<"YES";
    return 0;
}