#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;
    vector<int>arrx;
    vector<int>arry;
    for(int a0 = 0; a0 < n; a0++){
        int x;
        int y;
        cin >> x;
        arrx.push_back(x);
       cin >> y;
        arry.push_back(x);
    }
    int yes = 0;
    int i = 0;
    while(i < n-1){
        if(arrx[i] !=arrx[i+1])
            {
            yes = 1;
            break;
        }
        i++;
    }
    i = 0;
    int no = 0;
    while(i < n-1){
        if(arry[i] != arry[i+1]){
            no = 1;
            break;
        }
        i++;
    }
    if(yes == 1 || no ==1){
        cout << "NO";
    }
    else{
        cout << "YES";    
    }
    return 0;
}