#include<iostream>
using namespace std;
int main()
{
    int t;
    cin>>t;
    int count=0;
    for(int i=1;i<=t;i++)
    {
       int m,n;
        cin>>m>>n;
         if(m==0&&n!=0)
         {
           count++;
         }

        }

if(count==t)
        cout<<"YES"<<endl;
    else
        cout<<"NO"<<endl;

    return 0;
}