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 Microsoft.Win32.SafeHandles;
using System;
using System.Linq;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            var personCount = int.Parse(Console.ReadLine());
            var input = new int[personCount][][];
            for (int i = 0; i < personCount; i++)
            {
                input[i] = ReadPersonSaying();
            }

            int maxPattern = (int)Math.Pow(2, personCount);

            int max = 0;
            for (int i = 1; i < maxPattern; i++)
            {
                var bitArray = i.ToBitArray(personCount);
                if (CheckContradiction(bitArray, input))
                {
                    var honest = bitArray.Count(n => n == 1);
                    if (max < honest) { max = honest; }
                }
            }

            Console.WriteLine(max);
        }

        static bool CheckContradiction(int[] bitArray, int[][][] input)
        {
            bool result = true;

            for (var i = 0; i < bitArray.Length; i++)
            {
                if (bitArray[i] == 1)
                {
                    foreach (var x in input[i])
                    {
                        if (bitArray[x[0] - 1] != x[1])
                        {
                            result = false;
                        }
                    }
                }
            }

            return result;
        }

        static int[][] ReadPersonSaying()
        {
            var count = int.Parse(Console.ReadLine());
            var result = new int[count][];
            for (int i = 0; i < count; i++)
            {
                result[i] = Console.ReadLine().Split(' ').Select(str => int.Parse(str)).ToArray();
            }
            return result;
        }

    }

    static class Util
    {
        /// <summary>
        /// 指定の桁のビットを取得します。
        /// </summary>
        /// <param name="num"></param>
        /// <param name="count">取得する桁。</param>
        /// <returns></returns>
        public static int GetBit(this int num, int count)
        {
            int mask = (int)Math.Pow(2, count - 1);
            return (num & mask) == 0 ? 0 : 1;
        }

        /// <summary>
        /// <c>int</c>を2進数ビット配列に変換します。
        /// </summary>
        /// <param name="num"></param>
        /// <returns></returns>
        public static int[] ToBitArray(this int num, int keta)
        {
            var array = new int[keta];
            for (int i = 0; i < keta; i++)
            {
                array[i] = num.GetBit(i + 1);
            }
            return array;
        }

        /// <summary>
        /// <c>int</c>を2進数ビット配列に変換します。
        /// </summary>
        /// <param name="num"></param>
        /// <returns></returns>
        public static int[] ToBitArray(this int num) => ToBitArray(sizeof(int) * 8);

    }
}