#include<bits/stdc++.h>

#define s(a) scanf("%d",&a)
#define ss(a) scanf("%s",a)

#define MP           make_pair
#define PB           push_back
#define REP(i, n)    for(int i = 0; i < n; i++)
#define INC(i, a, b) for(int i = a; i <= b; i++)
#define DEC(i, a, b) for(int i = a; i >= b; i--)
#define CLEAR(a)     memset(a, 0, sizeof a)

using namespace std;

typedef long long          LL;
typedef unsigned long long ULL;
typedef vector<int>        VI;
typedef pair<int, int>     II;
typedef vector<II>         VII;

int main()
{
      int n;
      II inp[20];
      s(n);
      REP(i,n)
      {
            s(inp[i].first);
            s(inp[i].second);
      }
      INC(i,-10,10)
      {
            bool f = false;
            REP(j,n)
                  if(inp[j].first!=i)f = true;
            if(!f){cout<<"YES\n";return 0;}
            f = false;
            REP(j,n)
                  if(inp[j].second!=i)f = true;
            if(!f){cout<<"YES\n";return 0;}
      }
      {cout<<"NO\n";return 0;}

      return 0;
}