using System;
using System.Linq;
using System.Collections.Generic;
using Debug = System.Diagnostics.Trace;
using SB = System.Text.StringBuilder;
using static System.Math;
using static Program.IO.Scanner;
using Number = System.Int64;
using System.Numerics;

	using RMQ = SegmentTree<long, MaxData>;
#region IO
namespace Program.IO {
	using System.IO;
	using System.Text;
	using System.Globalization;

	public class Printer : StreamWriter {
		public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
		public Printer(Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
	}
	static public class Scanner {
		public static StreamScanner sc = new StreamScanner(Console.OpenStandardInput());
		public static int ri => sc.Integer();
		public static long rl => sc.Long();
		public static string rs => sc.Scan();
		public static double rd => sc.Double();
	}
	public class StreamScanner {
		public StreamScanner(Stream stream) { str = stream; }

		public readonly Stream str;
		private readonly byte[] buf = new byte[1024];
		private int len, ptr;
		public bool isEof = false;
		public bool IsEndOfStream { get { return isEof; } }

		private byte read() {
			if (isEof) return 0;
			if (ptr >= len) {
				ptr = 0;
				if ((len = str.Read(buf, 0, 1024)) <= 0) {
					isEof = true;
					return 0;
				}
			}
			return buf[ptr++];
		}

		public char Char() {
			byte b = 0;
			do b = read(); while ((b < 33 || 126 < b) && !isEof);
			return (char)b;
		}
		public string Scan() {
			var sb = new StringBuilder();
			for (var b = Char(); b >= 33 && b <= 126; b = (char)read()) sb.Append(b);
			return sb.ToString();
		}
		public string ScanLine() {
			var sb = new StringBuilder();
			for (var b = Char(); b != '\n' && b != 0; b = (char)read()) if (b != '\r') sb.Append(b);
			return sb.ToString();
		}
		public long Long() { return isEof ? long.MinValue : long.Parse(Scan()); }
		public int Integer() { return isEof ? int.MinValue : int.Parse(Scan()); }
		public double Double() { return isEof ? double.NaN : double.Parse(Scan(), CultureInfo.InvariantCulture); }
	}

}

#endregion

#region main
static class Ex {
	static public string AsString(this IEnumerable<char> ie) { return new string(ie.ToArray()); }
	static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ") {
		return string.Join(st, ie);
	}

	static public void Main() {
		Console.SetOut(new Program.IO.Printer(Console.OpenStandardOutput()) { AutoFlush = false });
		var solver = new Program.Solver();
		var t = new System.Threading.Thread(solver.Solve, 50000000);
		t.Start();
		t.Join();
		//*/
		//solver.Solve();
		Console.Out.Flush();
	}
}
#endregion

namespace Program {
	public class Solver {
		Random rnd = new Random(0);
		public void Solve() {
			var n=ri;
			var a=Enumerate(n*3, x => ri-1);
			var dp =Enumerate(n, x => new int[n]);
			for (int i = 0; i < n; i++)	
			for (int j = 0; j < n; j++)dp[i][j]=-1000000000;
			var max=Enumerate(n, x => -1000000000);
			max[a[0]]=max[a[1]]=0;
			dp[a[0]][a[1]]=dp[a[1]][a[0]]=0;
			var res=0;
			for (int k = 2; k+3 < a.Length; k+=3){
				var u=new int[]{a[k],a[k+1],a[k+2]};
				var Q=new List<(int,int,int)>();
				Array.Sort(u);
				if(u[0]==u[2]) { res++; continue;}
				else if(u[0]==u[1]){
					for (int i = 0; i < n; i++)
						Q.Add((i,u[2],dp[i][u[0]]+1));

				}else if(u[1]==u[2]){
					for (int i = 0; i < n; i++)
						Q.Add((i,u[0],dp[i][u[2]]+1));
				}
				var ma  = max.Max();
				Q.Add((u[0],u[1],Max(ma,dp[u[2]][u[2]]+1)));
				Q.Add((u[0],u[2],Max(ma,dp[u[1]][u[1]]+1)));
				Q.Add((u[2],u[1],Max(ma,dp[u[0]][u[0]]+1)));
				for (int i = 0; i < n; i++)
					for (int id = 0; id < 3; id++)
					Q.Add((i,u[id],max[i]));
				foreach (var (x,y,v) in Q)
				{
					dp[x][y]=dp[y][x]=Max(dp[x][y],v);
					max[x]=Max(max[x],v);
					max[y]=Max(max[y],v);
				}
			}
			var ans=max.Max();
			ans=Max(ans,dp[a.Last()][a.Last()]+1);
			ans+=res;
			Console.WriteLine(ans);
			
		}
		const long INF = 1L << 60;
		static int[] dx = { -1, 0, 1, 0 };
		static int[] dy = { 0, 1, 0, -1 };
		static T[] Enumerate<T>(int n, Func<int, T> f) {
			var a = new T[n]; for (int i = 0; i < a.Length; ++i) a[i] = f(i); return a;
		}
		static T[][] Enumerate<T>(int n, int m, Func<int, int, T> f) {
			return Enumerate(n, x => Enumerate(m, y => f(x, y)));
		}
		static public void Swap<T>(ref T a, ref T b) { var tmp = a; a = b; b = tmp; }
	}
}
	#region SegTree Operator
	public interface IData<T> {
		T Merge(T l, T r);
		T Identity { get; }
	}
	#endregion
	#region Segment Tree

	public class SegmentTree<T, U>
	   where U : struct, IData<T> {
		int sz;
		int n;
		T[] data;
		U op;
		public SegmentTree(int size) {
			sz = size;
			n = 1;
			while (n < size) n *= 2;
			data = new T[n * 2];
			for (int i = 0; i < data.Length; i++)
				data[i] = op.Identity;
		}
		public SegmentTree(T[] a) {
			sz = a.Length;
			n = 1;
			while (n < sz) n *= 2;
			data = new T[n * 2];
			for (int i = 0; i < n; i++)
				data[i + n] = (i < a.Length) ? a[i] : op.Identity;
			for (int i = n - 1; i >= 0; i--)
				data[i] = op.Merge(data[i * 2], data[i * 2 + 1]);
		}
		public void Update(int k, T v) {
			k += n;
			data[k] = v;
			for (k = k / 2; k > 0; k /= 2)
				data[k] = op.Merge(data[k * 2], data[k * 2 + 1]);

		}
		public T Query(int a, int b) {
			T L = op.Identity, R = op.Identity;
			for (a += n, b += n; a < b; a /= 2, b /= 2) {
				if ((a & 1) == 1) L = op.Merge(L, data[a++]);
				if ((b & 1) == 1) R = op.Merge(data[--b], R);
			}
			return op.Merge(L, R);
		}
		public T[] Items {
			get {
				var ret = new T[sz];
				for (int i = 0; i < sz; i++)
					ret[i] = data[i + n];
				return ret;
			}
		}

	}
	#endregion
	#region RMQ

	public struct MaxData : IData<long> {
		public long Identity { get { return long.MinValue; } }
		public long Merge(long l, long r) { return Math.Max(l, r); }
	}
	#endregion


Measured memory_bytes: 71908