#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;
    int *x_coords;
    int *y_coords;
    x_coords = new int[n];
    y_coords = new int[n];
    for(int a0 = 0; a0 < n; a0++){
        int x;
        int y;
        cin >> x >> y;
        x_coords[a0] = x;
        y_coords[a0] = y;
    }
    
    int flag = -1; //1 - vert 2-horiz
    int horiz_flag = 0;
    int vert_flag = 0;
    for ( int i = 0; i < n; i++) {
        if ( flag == -1 ) {

            horiz_flag = x_coords[i];
            vert_flag  = y_coords[i];
            flag = 0;
        };
        if ( flag == 0 ) {
            
            if ( x_coords[i] != horiz_flag && y_coords[i] != vert_flag ) { cout << "NO"; return 1; }
            
            if ( x_coords[i] != horiz_flag ) {
        
                flag = 1;
            };
            if ( y_coords[i] != vert_flag ) {
                
                flag = 2;
            }
        }
        
        if ( flag == 1 && y_coords[i] != vert_flag ) { cout << "NO"; return 1; }
        if ( flag == 2 && x_coords[i] != horiz_flag ) { cout << "NO"; return 1; }
    }
    
    cout << "YES";
    return 0;
}