#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,countx=0,county=0;
    cin >> n;
            int x;
        int y;
        cin >> x >> y;
    int temp=x,temp2=y;
    for(int a0 = 0; a0 < n-1; a0++){

        cin >> x >> y;
        if(x==temp){
      countx++;

        }
        if(y==temp2){
            county++;
        }
                if(countx!=a0+1 && county!=a0+1){
            cout <<"NO" << endl;
            return 0;
        }
    }
    cout << "YES" << endl;
    return 0;
}