#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, a, b, flag = 3;
    cin >> n;
    for(int a0 = 0; a0 < n; a0++){
        int x;
        int y;
        cin >> x >> y;
        if(a0==0)
        {
            a = x; b = y;
        }
        else if(a0==1)
        {
            if(a==x) flag=1;
            else if(b==y) flag = 2;
            else flag = 0;
        }
        else
        {
            if(flag==1&&x!=a) flag = 0;
            else if(flag==2&&y!=b) flag = 0;
        }
    }
    if(flag==0) cout<<"NO"<<endl;
    else cout<<"YES"<<endl;
    return 0;
}