#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main()
{
    int n=0,i=0,j=0,arr[10][2],x=1;
    scanf("%d",&n);
    while(i<n)
    {
        for(j=0;j<2;j++)
            scanf("%d",&arr[i][j]);
        i++;
    }
    i=1,j=arr[0][0];
    while(i<n)
    {
        if(j!=arr[i][0])
        {
            x=0;
            break;
        }
        i++;
    }
    if(x==1)
        printf("YES");
    else
    {
        x=1;
        j=arr[0][1];
        i=1;
        while(i<n)
        {
            if(j!=arr[i][1])
            {
                x=0;
                break;
            }
            i++;
        }
        if(x==1)
            printf("YES");
        else
            printf("NO");
    }
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */
    return 0;
}