#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,i,j,count=0;
    cin>>n;
   int x[n],y[n];
    for(i=0;i<n;i++)
        cin>>x[i]>>y[i];
    for(i=0;i<n-1;i++)
        {
        for(j=i+1;j<n;j++)
            {
            if((x[i]!=x[j])&&(y[i]!=y[j]))
               {
                   count=1;
                   break;
               }
        }
               if(count)
               break;
    }
    if(count)
        cout<<"NO\n";
    else
        cout<<"YES\n";
    return 0;
}