#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,p1,p2,h=0;
    cin >> n;
    for(int a0 = 0; a0 < n; a0++){
        int x;
        int y;
       
        cin >> x >> y;
        if(a0==0)
            {
            p1=x;
            p2=y;
        }else{
        if(h==0)
        {
            if(x==p1&&y!=p2)
                {

                h=1;
            }
            else if(x!=p1&&y==p2)
                {

                h=2;
            }
            else if(x!=p1&&y!=p2){
                    cout<<"NO\n";
                return 0;
            }
        }
    else
        {
        if(h==1)
            {
            if(x!=p1)
                {
                cout<<"NO\n";
                return 0;
            }
        }
        if(h==2)
            {
            if(y!=p2)
                {
                cout<<"NO\n";
                return 0;
            }
        }
    }
        
        } 
        
    }
//    if(h==0)
            cout<<"YES\n";
 //  cout<<"NO\n";
    return 0;
}