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.Linq;//リストの使用
using System.Collections.Generic;
using System.Text;//テキストの高速出力に必要
class Program
{
	static void Main()
	{
		int n = int.Parse(Console.ReadLine());
    int answer = 0;
    int[][] vertexes = new int[n][];
    for(int i = 0; i < n; i++)
    {
      int cc = int.Parse(Console.ReadLine());
      vertexes[i] = new int[cc*2];
      for(int j = 0; j < cc; j++)
      {
        string[] input = Console.ReadLine().Split(' ');
        vertexes[i][2*j] = int.Parse(input[0])-1;
        vertexes[i][2*j+1] = int.Parse(input[1]);
      }
    }

    for(long i = 0; i < (1 << (int)n); i++)//bit全探索
    {
      bool truee = true;
      for(long checkDigit = 0; checkDigit < n; checkDigit++)//右からcheckDigit桁目を見る
      {
        if((i & (1<<(int)checkDigit)) != 0)//右からcheckDigit番目が1ならば
        {
          //checkDigit番目の操作

          for(int j = 0; j < vertexes[checkDigit].Length/2; j++)
          {
            if(vertexes[checkDigit][2*j+1] != (i & (1<<(vertexes[checkDigit][2*j]))))
            {
              truee = false;
            }
          }
        }
      }

      if(truee)
      {
        //Console.WriteLine(i);
        int answerMemo = 0;
        for(long checkDigit = 0; checkDigit < n; checkDigit++)//右からcheckDigit桁目を見る
        {
          if((i & (1<<(int)checkDigit)) != 0)//右からcheckDigit番目が1ならば
          {
            answerMemo++;
          }
        }
        answer = Math.Max(answer,answerMemo);
      }
    }

    Console.WriteLine(answer);
	}
}