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: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Practice
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            int[][] table = new int[n][] ;
   
            //証言の表の作成
            for(int i = 0; i < n; i++)
            {
                int a = int.Parse(Console.ReadLine());
                table[i] = new int[a];
                for(int j = 0; j < a; j++)
                {
                    string[] str = Console.ReadLine().Split(' ');
                    int x = int.Parse(str[0]);
                    int y = int.Parse(str[1]);
                    if (y == 1) {table[i][j] = x;}
                    else { table[i][j] = -x; }
                }
            }



            double max = 0;

            //以下各パターンにおいて矛盾がないか調べる
            for(int i = 1; i < (Math.Pow(2,n)); i++)
            {
                double[] X = new double[n];
                int p = i;
                for(int q = n-1; q >= 0; q--)
                {
                    if (p >= (int)(Math.Pow(2, q)))
                    {
                        X[q] = 1;
                        p -= (int)(Math.Pow(2, q));
                    }
                    else {
                        X[q] = 0;
                    }
                }



                for (int xi = 0; xi < n; xi++)
                {
                    if (X[xi] != 0)
                    {
                        for (int yi = 0; yi < table[xi].Length; yi++)
                        {
                            if (((table[xi][yi]>0 ^ X[Math.Abs(table[xi][yi])-1] ==0))==false)
                            {
                                goto badend;
                            }
                        }
                    }
                }
                    if(X.Sum()>max)
                    {
                        max = X.Sum();
                    }
            badend:;

            }

            Console.WriteLine(max);

            //ここまで
        }
    }
}