using System;
using System.Collections.Generic;

public class Program
{
    private int N;
    private int[] A;
    private int[][] Y;

    public void Solve()
    {
        var sc = new Scanner();
        N = sc.NextInt();
        A = new int[N];
        Y = new int[N][];

        for (int i = 0; i < N; i++)
        {
            A[i] = sc.NextInt();
            Y[i] = new int[N];
            for (int j = 0; j < A[i]; j++)
            {
                int x = sc.NextInt() -1;
                Y[i][x] = sc.Next() == "1" ? 1 : -1;
            }
        }

        var l = 1 << N;
        int ans = 0;
        for (int i = 0; i < l; i++)
        {
            int cnt = 0;
            int cp = i;
            bool f = true;
            for (int j = 0; cp > 0; j++)
            {
                if (cp % 2 == 1)
                {
                    cnt++;
                    for (int k = 0; k < N; k++)
                    {
                        if (Y[j][k] != 0)
                        {
                            // jがkを正直者と言っている
                            bool a = Y[j][k] == 1;

                            bool b = (i & (1 << (k))) > 0;
                            if (a != b)
                            {
                                f = false;
                                break;
                            }
                        }
                    }

                    if (!f)
                    {
                        break;
                    }
                }

                cp /= 2;
            }

            if (f)
            {
                ans = Math.Max(cnt, ans);
            }
        }
        
        Console.WriteLine(ans);
    }

    public static void Main(string[] args)
    {
        new Program().Solve();
    }
}

class Scanner
{
    public Scanner()
    {
        _pos = 0;
        _line = new string[0];
    }

    const char Separator = ' ';
    private int _pos;
    private string[] _line;

    #region スペース区切りで取得

    public string Next()
    {
        if (_pos >= _line.Length)
        {
            _line = Console.ReadLine().Split(Separator);
            _pos = 0;
        }

        return _line[_pos++];
    }

    public int NextInt()
    {
        return int.Parse(Next());
    }

    public long NextLong()
    {
        return long.Parse(Next());
    }

    public double NextDouble()
    {
        return double.Parse(Next());
    }

    #endregion

    #region 型変換

    private int[] ToIntArray(string[] array)
    {
        var result = new int[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = int.Parse(array[i]);
        }

        return result;
    }

    private long[] ToLongArray(string[] array)
    {
        var result = new long[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = long.Parse(array[i]);
        }

        return result;
    }

    private double[] ToDoubleArray(string[] array)
    {
        var result = new double[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = double.Parse(array[i]);
        }

        return result;
    }

    #endregion

    #region 配列取得

    public string[] Array()
    {
        if (_pos >= _line.Length)
            _line = Console.ReadLine().Split(Separator);

        _pos = _line.Length;
        return _line;
    }

    public int[] IntArray()
    {
        return ToIntArray(Array());
    }

    public long[] LongArray()
    {
        return ToLongArray(Array());
    }

    public double[] DoubleArray()
    {
        return ToDoubleArray(Array());
    }

    #endregion
}

Measured memory_bytes: 13268