#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,i;
    cin >> n;
    bool t = true;
    int arr[n][n] = {0};
    for(int a0 = 0; a0 < n; a0++){
        //int x;
        //int y;
        cin >> arr[a0][0] >> arr[a0][1];
    }
    int chk = 2;
    for(i=1;i<n;i++){
        if(arr[i][0] != arr[i-1][0] && arr[i][1] != arr[i-1][1]){
            break;
        }
        if(chk == 2){
            if(arr[i][0] != arr[i-1][0]){
                chk = 1;
            }
            if(arr[i][1] != arr[i-1][1]){
                chk = 0;
            }            
        }
        else if(chk == 0){
            if(arr[i][0] != arr[i-1][0]){
                break;
            }
        }
        else if(chk == 1){
            if(arr[i][1] != arr[i-1][1]){
                break;
            }
        }
    }
    if(i==n){
        cout<<"YES";
    }
    else{
        cout<<"NO";
    }
    
    return 0;
}