#include<bits/stdc++.h>
using namespace std;
int main()
{
    long long int i,j,k,a[100],b[100],n;
    while(cin>>n)
    {
        j=k=1;
        for(i=0;i<n;i++)
        {
            cin>>a[i]>>b[i];
            if(i>0 and a[i-1]!=a[i]) j=0;
            if(i>0 and b[i-1]!=b[i]) k=0;
        }
        if(j==1 || k==1) cout<<"YES"<<endl;
        else cout<<"NO"<<endl;
    }
    return 0;
}