#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,k=0;
    cin >> n;
    int x[n],y[n];
    for(int i= 0; i < n; i++){
        
        cin >> x [i]>> y[i];
    }
     for(int i= 0; i < n-1; i++){
         if(x[i]!=x[i+1]&&y[i]==y[i+1])
             k++;
         else if(x[i]==x[i+1]&&y[i]!=y[i+1])
             k++;
     }
             if(k==n-1)
             cout<<"YES";
    else
        cout<<"NO";
             
    return 0;
}