#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>

int main(){
    int n; 
    scanf("%d",&n);
    int sx,sy;
    int f = 0, flag = 1;
    for(int a0 = 0; a0 < n; a0++){
        int x; 
        int y; 
        scanf("%d %d",&x,&y);
        if(a0 == 0){
            sx = x;
            sy = y;
        }
        else if(a0 == 1){
            if(x == sx){
                f = 1;
            }
            else if(y == sy){
                f = 2;
            }
            else{
                flag = 0;
                break;
            }
        }
        else{
            if(sx == x && f == 1){
                continue;
            }
            else if(sy == y && f == 2){
                continue;
            }
            else{
                flag = 0;
                break;
            }
        }
    }
    if(flag == 0){
        printf("NO\n");
    }
    else{
        printf("YES\n");
    }
    return 0;
}