#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;
    if(n<2 || n>10){
        cout<<"NO";
        return 0;
    }
    int first=0;
    int yes=0;
    int search_x=0;
    int sx=0;
    int sy=0;
    int search_y=0;
    for(int a0 = 0; a0 < n; a0++){
        int x;
        int y;
         cin >> x >> y;
        if(x>10 || x<-10 || y>10 || y<-10){
            yes=1;
            break;
        }
       else if(first==0){
           search_x=x;
           search_y=y;
           first=1;
            
        }
        else if(first==1){
            if(x==search_x){
                first=2;
                sx=1;
            }
            else if(y==search_y){
                first=2;
                sy=1;
            }
            else{
                yes=1;
                break;
            }
                
    }
        else if(first==2){
            if(sx==1){
                if(x != search_x){
                    yes=1;
                    break;
                }
            }
            else if(sy==1){
                if(y != search_y){
                yes=1;
                break;
                }
            }
                
           
        }
    }
    if(yes==0 )
        cout<<"YES";
    else
        cout<<"NO";
    return 0;
}