#include<bits/stdc++.h>

using namespace std;

int main()
{
    int t,ck=1;
    cin>>t;
    while(t--){
        int x,y;
        cin>>x>>y;
        if( x!=0 && y!=0 ){
            ck=0;
        }
    }
    if(ck==0){
        printf("NO\n");
    }
    else if(ck==1)
        cout<<"YES"<<endl;

    return 0;
}