#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,x,y;
    cin >> n;
        cin >> x >> y; int a=x;int b=y;int ok1=0;int ok2=0;
    for(int a0 = 0; a0 < n; a0++){
        cin >> x >> y;
        if(x!=a)ok1=1;
        if(y!=b)ok2=1;
       
    }
    if(ok1==0||ok2==0)cout<<"YES";else cout<<"NO";return 0;
}