Problem:
Score : 300 points

Problem Statement

There are N people numbered 1 to N. Each of them is either an honest person whose testimonies are always correct or an unkind person whose testimonies may be correct or not.

Person i gives A_i testimonies. The j-th testimony by Person i is represented by two integers x_{ij} and y_{ij}. If y_{ij} = 1, the testimony says Person x_{ij} is honest; if y_{ij} = 0, it says Person x_{ij} is unkind.

How many honest persons can be among those N people at most?

Constraints

All values in input are integers.

1 \leq N \leq 15

0 \leq A_i \leq N - 1

1 \leq x_{ij} \leq N

x_{ij} \neq i

x_{ij_1} \neq x_{ij_2} (j_1 \neq j_2)

y_{ij} = 0, 1

Input

Input is given from Standard Input in the following format:

N
A_1
x_{11} y_{11}
x_{12} y_{12}
:
x_{1A_1} y_{1A_1}
A_2
x_{21} y_{21}
x_{22} y_{22}
:
x_{2A_2} y_{2A_2}
:
A_N
x_{N1} y_{N1}
x_{N2} y_{N2}
:
x_{NA_N} y_{NA_N}

Output

Print the maximum possible number of honest persons among the N people.

Sample Input 1

3
1
2 1
1
1 1
1
2 0

Sample Output 1

2

If Person 1 and Person 2 are honest and Person 3 is unkind, we have two honest persons without inconsistencies, which is the maximum possible number of honest persons.

Sample Input 2

3
2
2 1
3 0
2
3 1
1 0
2
1 1
2 0

Sample Output 2

0

Assuming that one or more of them are honest immediately leads to a contradiction.

Sample Input 3

2
1
2 0
1
1 0

Sample Output 3

1

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;

namespace abc147_c
{
  class Program
  {
    static void Main(string[] args)
    {
      var n = CIn.ReadInt();
      var p = new Person[n];

      for (var i = 0; i < n; i++)
      {
        var a = CIn.ReadInt();
        var t = new Testimony[a];

        for (var j = 0; j < a; j++)
        {
          var x = CIn.ReadInt() - 1;
          var y = CIn.ReadInt();

          t[j] = new Testimony(x, y);
        }

        p[i] = new Person(t);
      }

      var ans = 0;

      for (var i = (int)Math.Pow(2, n) - 1; i >= 0; i--)
      {
        var b = Convert.ToString(i, 2).Select(s => s == '1').Reverse().ToArray();
        var f = true;

        for (var j = 0; j < b.Length; j++)
        {
          if (b[j])
          {
            foreach (var t in p[j].Testimonies)
            {
              if (!(t.Number < b.Length && b[t.Number] == t.IsHonest))
              {
                f = false;
              }
            }
          }
        }

        if (f)
        {
          ans = Math.Max(ans, b.Count(e => e));
        }
      }

      Console.WriteLine(ans);
    }
  }

  class Person
  {
    private Testimony[] _testimonies;
    public IReadOnlyCollection<Testimony> Testimonies { get { return _testimonies; } }
    
    public Person(Testimony[] t)
    {
      _testimonies = t;
    }
  }

  class Testimony
  {
    public int Number { get; }
    public bool IsHonest { get; }

    public Testimony(int n, int h)
    {
      Number = n;
      IsHonest = h == 1;
    }
  }

  class CIn
  {
    private static readonly Queue<string> fieldBuffer = new Queue<string>();

    public static string Read()
    {
      if (fieldBuffer.Count == 0)
      {
        foreach (var field in Console.ReadLine().Split())
        {
          fieldBuffer.Enqueue(field);
        }
      }
      return fieldBuffer.Dequeue();
    }

    public static int ReadInt() => int.Parse(Read());
    public static long ReadLong() => long.Parse(Read());
    public static double ReadDouble() => double.Parse(Read());

    public static string[] ReadStringArray(long n)
    {
      var array = new string[n];
      for (var i = 0; i < n; i++)
      {
        array[i] = Read();
      }
      return array;
    }

    public static int[] ReadIntArray(long n)
    {
      var array = new int[n];
      for (var i = 0; i < n; i++)
      {
        array[i] = ReadInt();
      }
      return array;
    }

    public static long[] ReadLongArray(long n)
    {
      var array = new long[n];
      for (var i = 0; i < n; i++)
      {
        array[i] = ReadLong();
      }
      return array;
    }

    public static double[] ReadDoubleArray(long n)
    {
      var array = new double[n];
      for (var i = 0; i < n; i++)
      {
        array[i] = ReadDouble();
      }
      return array;
    }
  }
}