using System;
using System.Collections.Generic;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.IO;
using System.Reflection;
using static System.Math;
using System.Numerics;
using System.Threading;
using System.Runtime.CompilerServices;
using System.Diagnostics;
static class Program{
	const long inf=long.MaxValue>>1;
	const int mod=(int)1e9+7;
	static Sc sc=new Sc();
	static Pt pt=new Pt();
	static void Main(){
		Solve();
		pt.Sm();
	}
	static void Solve() {
		var n=sc.I;
		var a=new int[101,101];
		var h=new int[n][];
		int p=0;
		for(int i = 0;i<n;i++) {
			h[i]=sc.Ia;
			if(a[h[i][0],h[i][1]]==0){a[h[i][0],h[i][1]]=++p;}
			if(a[h[i][2],h[i][3]]==0){a[h[i][2],h[i][3]]=++p;}
		}
		var fl=new Mfp((p<<1)+n+3);
		for(int i = 0;i<n;i++) {
			fl.Edge(a[h[i][0],h[i][1]],a[h[i][2],h[i][3]]+p,1);
			fl.Edge(a[h[i][0],h[i][1]]+p,a[h[i][2],h[i][3]]+p,1);
			fl.Edge(0,(p<<1)+1+i,1);
			fl.Edge((p<<1)+1+i,a[h[i][0],h[i][1]],1);
			fl.Edge((p<<1)+1+i,a[h[i][2],h[i][3]],1);
		}
		for(int i = 1;i<=p;i++) {fl.Edge(p+i,(p<<1)+n+1,1);}
		pt.Wl(fl.Dinic(0,(p<<1)+n+1)==n?"YES":"NO");
	}
}
public class Mfp{
	public List<int>[] li;
	private Dictionary<int,int>[] h;
	private bool[] b;
	private int[] l;
	private int n,ans,go;
	private const int inf=int.MaxValue;
	public Mfp(int n){
		this.n=n;
		li=new List<int>[n];
		h=new Dictionary<int,int>[n+1];
		for(int i=0;i<n;i++){
			li[i]=new List<int>();
			h[i]=new Dictionary<int,int>();
		}
	}
	public void Edge(int a,int b,int c){
		if(a==b){return;}
		if(!h[a].ContainsKey(b)){
			li[a].Add(b);
			li[b].Add(a);
			h[a].Add(b,c);
			h[b].Add(a,0);
		}
		else{h[a][b]+=c;}
	}
	public int Dinic(int st,int go){
		this.go=st;
		ans=0;
		int z=1;
		while(z>0){
			l=new int[n];
			var qu=new Queue<ValueTuple<int,int>>();
			qu.Enqueue(ValueTuple.Create(st,1));
			l[st]=1;
			while(qu.Count>0){
				var e=qu.Dequeue();
				for(int i=0;i<li[e.Item1].Count;i++){
					if(l[li[e.Item1][i]]==0&&h[e.Item1][li[e.Item1][i]]!=0){
						l[li[e.Item1][i]]=e.Item2+1;
						qu.Enqueue(ValueTuple.Create(li[e.Item1][i],e.Item2+1));
					}
				}
				if(e.Item1==go){break;}
			}
			b=new bool[n];
			z=Fu3(go,inf);
			ans+=z;
		}
		return ans;
	}
	private int Fu3(int a,int p){
		if(a==go){return p;}
		int u=0;
		for(int i=0;i<li[a].Count&&p>u;i++){
			if(!b[li[a][i]]&&l[li[a][i]]<l[a]&&h[li[a][i]][a]!=0){
				int z=Fu3(li[a][i],Min(p-u,h[li[a][i]][a]));
				h[li[a][i]][a]-=z;
				h[a][li[a][i]]+=z;
				u+=z;
			}
		}
		if(u==0){b[a]=true;}
		return u;
	}
	public int Ff(int st,int go){
		this.go=go;
		ans=0;
		int z=1;
		while(z>0){
			b=new bool[n];
			z=Fu2(st,inf);
			ans+=z;
		}
		return ans;
	}
	private int Fu2(int a,int p){
		if(a==go){return p;}
		int u=0;
		b[a]=true;
		for(int i=0;i<li[a].Count&&p>u;i++){
			if(!b[li[a][i]]&&h[a][li[a][i]]!=0){
				int z=Fu2(li[a][i],Min(p-u,h[a][li[a][i]]));
				h[a][li[a][i]]-=z;
				h[li[a][i]][a]+=z;
				u+=z;
			}
		}
		if(u!=0){b[a]=false;}
		return u;
	}
	public void Vc(int s,Action<int> f){
		b=new bool[n];
		Fu4(s,0,f);
		for(int i=0;i<li[s].Count;i++){
			if(h[s][li[s][i]]==0&&!b[li[s][i]]){f(li[s][i]);}
		}
	}
	private void Fu4(int a,int p,Action<int> f){
		b[a]=true;
		if((p&1)==0&&p!=0){f(a);}
		for(int i=0;i<li[a].Count;i++){
			if(h[a][li[a][i]]!=0&&!b[li[a][i]]){Fu4(li[a][i],p+1,f);}
		}
	}
}
public class Pt{
	private StringBuilder sb=new StringBuilder();
	public void W(int s){sb.Append(s);}
	public void W(long s){sb.Append(s);}
	public void W(double s){sb.Append(s);}
	public void W(decimal s){sb.Append(s);}
	public void W(string s){sb.Append(s);}
	public void W(object s){sb.Append(s);}
	public void W(string f,int s){sb.Append(s.ToString(f));}
	public void W(string f,long s){sb.Append(s.ToString(f));}
	public void W(string f,double s){sb.Append(s.ToString(f));}
	public void W(string f,decimal s){sb.Append(s.ToString(f));}
	public void Wl(int s){sb.Append(s).Append(Environment.NewLine);}
	public void Wl(long s){sb.Append(s).Append(Environment.NewLine);}
	public void Wl(double s){sb.Append(s).Append(Environment.NewLine);}
	public void Wl(decimal s){sb.Append(s).Append(Environment.NewLine);}
	public void Wl(string s){sb.Append(s).Append(Environment.NewLine);}
	public void Wl(object s){sb.Append(s).Append(Environment.NewLine);}
	public void Wl(string f,int s){sb.Append(s.ToString(f)).Append(Environment.NewLine);}
	public void Wl(string f,long s){sb.Append(s.ToString(f)).Append(Environment.NewLine);}
	public void Wl(string f,double s){sb.Append(s.ToString(f)).Append(Environment.NewLine);}
	public void Wl(string f,decimal s){sb.Append(s.ToString(f)).Append(Environment.NewLine);}
	public void Wl(int[] s){sb.Append(string.Join(" ",s)).Append(Environment.NewLine);}
	public void Wl(long[] s){sb.Append(string.Join(" ",s)).Append(Environment.NewLine);}
	public void Wl(double[] s){sb.Append(string.Join(" ",s)).Append(Environment.NewLine);}
	public void Wl(string[] s){sb.Append(string.Join(" ",s)).Append(Environment.NewLine);}
	public void Wl(object[] s){sb.Append(string.Join(" ",s)).Append(Environment.NewLine);}
	public void Wl(){sb.Append(Environment.NewLine);}
	public void Sm(){Console.Write(sb);}
}
public class Sc{
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	protected virtual string Rl(){return Console.ReadLine();}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	protected virtual string[] Sp(string st){return st.Split();}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	private T Ct<T>(string s){return (T)Convert.ChangeType(s,typeof(T));}
	public virtual int I{get{return int.Parse(Rl());}}
	public virtual long L{get{return long.Parse(Rl());}}
	public virtual double D{get{return double.Parse(Rl());}}
	public virtual string S{get{return Rl();}}
	public int[] Ia{get{return Array.ConvertAll(Sp(Rl()),int.Parse);}}
	public long[] La{get{return Array.ConvertAll(Sp(Rl()),long.Parse);}}
	public double[] Da{get{return Array.ConvertAll(Sp(Rl()),double.Parse);}}
	public string[] Sa{get{return Sp(Rl());}}
	public object[] Oa{get{return Sp(Rl());}}
	public int[] Ia2{get{return Array.ConvertAll(Sp("0 "+Rl()+" 0"),int.Parse);}}
	public int[] Ia3(string a,string b){return Array.ConvertAll(Sp(a+Rl()+b),int.Parse);}
	public int[] Ia3(int a){return Array.ConvertAll(Sp(Rl()+" "+a.ToString()),int.Parse);}
	public long[] La2{get{return Array.ConvertAll(Sp("0 "+Rl()+" 0"),long.Parse);}}
	public long[] La3(string a,string b){return Array.ConvertAll(Sp(a+Rl()+b),long.Parse);}
	public long[] La3(int a){return Array.ConvertAll(Sp(Rl()+" "+a.ToString()),long.Parse);}
	public double[] Da2{get{return Array.ConvertAll(Sp("0 "+Rl()+" 0"),double.Parse);}}
	public double[] Da3(string a,string b){return Array.ConvertAll(Sp(a+Rl()+b),double.Parse);}
	public T[] Arr<T>(int n,Func<T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f();}return a;}
	public T[] Arr<T>(int n,Func<int,T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i);}return a;}
	public T[] Arr<T>(int n,Func<string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(Sp(Rl()));}return a;}
	public T[] Arr<T>(int n,Func<int,string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i,Sp(Rl()));}return a;}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public (T,T) Tp2<T>(){var s=Sp(Rl());return (Ct<T>(s[0]),Ct<T>(s[1]));}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public (T,T,T) Tp3<T>(){var s=Sp(Rl());return (Ct<T>(s[0]),Ct<T>(s[1]),Ct<T>(s[2]));}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public (T,T,T,T) Tp4<T>(){var s=Sp(Rl());return (Ct<T>(s[0]),Ct<T>(s[1]),Ct<T>(s[2]),Ct<T>(s[3]));}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public (T,T,T,T,T) Tp5<T>(){var s=Sp(Rl());return (Ct<T>(s[0]),Ct<T>(s[1]),Ct<T>(s[2]),Ct<T>(s[3]),Ct<T>(s[4]));}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public (T,T,T,T,T,T) Tp6<T>(){var s=Sp(Rl());return (Ct<T>(s[0]),Ct<T>(s[1]),Ct<T>(s[2]),Ct<T>(s[3]),Ct<T>(s[4]),Ct<T>(s[5]));}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public (T1,T2) Tp2<T1,T2>(){var s=Sp(Rl());return (Ct<T1>(s[0]),Ct<T2>(s[1]));}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public (T1,T1,T2) Tp3<T1,T2>(){var s=Sp(Rl());return (Ct<T1>(s[0]),Ct<T1>(s[1]),Ct<T2>(s[2]));}
}
public class Scs:Sc{
	private StreamReader sr;
	public Scs(string t){sr=new StreamReader(t);}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	protected override string Rl(){return sr.ReadLine();}
}
public class Sc2:Sc{
	private string[] sps=new string[]{" ","　","\t"};
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	protected override string[] Sp(string st){return st.Split(sps,StringSplitOptions.RemoveEmptyEntries);}
	public override int I{get{return int.Parse(Sp(Rl())[0]);}}
	public override long L{get{return long.Parse(Sp(Rl())[0]);}}
	public override double D{get{return double.Parse(Sp(Rl())[0]);}}
	public override string S{get{return Sp(Rl())[0];}}
}
public class Scs2:Sc2{
	private StreamReader sr;
	public Scs2(string t){sr=new StreamReader(t);}
	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	protected override string Rl(){return sr.ReadLine();}
}
public class Sct:Sc{
	private List<string> li=new List<string>();
	private int l=0;
	public void Add(int s){li.Add(s.ToString());}
	public void Add(long s){li.Add(s.ToString());}
	public void Add(double s){li.Add(s.ToString());}
	public void Add(string s){li.Add(s.ToString());}
	public void Add(object s){li.Add(s.ToString());}
	public void Add(int[] s){li.Add(string.Join(" ",s));}
	public void Add(long[] s){li.Add(string.Join(" ",s));}
	public void Add(double[] s){li.Add(string.Join(" ",s));}
	public void Add(string[] s){li.Add(string.Join(" ",s));}
	public void Add(object[] s){li.Add(string.Join(" ",s));}
	protected override string Rl(){return li[l++];}
	public void Clear(){li.Clear();l=0;}
}