#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#define f(i,s,n) for(int i=s;i<n;i++)
#define sd(n) scanf("%d",&n)
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */ 
    int n; sd(n);
    int x,y; sd(x); sd(y);
    int u=x,v=y,a;
    sd(x); sd(y);
    if(x==u) a=1;
    else if(y==v) a=2;
    else a=0;
    while(n>2){
        sd(x); sd(y);
        if(a==1 && x!=u) {
            a=0;
            break;
        }
        else if(a==2 && y!=v){
            a=0;
            break;
        }
        n--;
    }
    if(a==0) printf("NO");
    else printf("YES");
    return 0;
}