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.Diagnostics;
using System.Linq;

namespace PaizaTest
{
    class Program
    {
        static void Main(string[] args)
        {
            var N = int.Parse(Console.ReadLine());
            //var allPatterns = new List<List<Tuple<int, int>>>();
            var allPatterns = Enumerable.Range(0, N).Select(_ => new List<Tuple<int, int>>()).ToList();

            for (int i = 0; i < N; i++)
            {
                var evidences = new List<Tuple<int, int>>();
                var a = int.Parse(Console.ReadLine());
                for (int j = 0; j < a; j++)
                {
                    var oneLine = Console.ReadLine().Split(' ').Select(int.Parse).ToList();
                    evidences.Add(new Tuple<int, int>(oneLine[0], oneLine[1]));
                }
                //allPatterns.Add(evidences);
                allPatterns[i] = evidences;
            }

            var max = 0;
            for (int i = 0; i < Math.Pow(2, N); i++)
            {
                var ok = true;
                // 全パターンを試す
                for (int j = 0; j < allPatterns.Count; j++)
                {
                    // 現在の番号の人が不親切である場合、証言は気にしないので次の人へ
                    if (((i >> j) & 1) != 1)
                    {
                        continue;
                    }

                    var aPeople = allPatterns[j];
                    for (int k = 0; k < aPeople.Count; k++)
                    {
                        // まずiを2進数化する
                        // それぞれを証言と突き合わせていく
                        var evidence = aPeople[k];
                        // 人は1～15の番号が与えられている
                        // ので、番号-1桁が対象の状態になる
                        var targetPeople = evidence.Item1;
                        // 証言の内容を取得
                        var isHonest = evidence.Item2;
                        // 対象の人の状態を取得
                        var targetPeopleStatus = (i >> (targetPeople - 1)) & 1;
                        // 対象の人の状態と証言が一致していなければ、okにfalseを入れる
                        if ((targetPeopleStatus ^ isHonest) == 1)
                        {
                            ok = false;
                        }
                    }
                }

                if (ok)
                {
                    max = Math.Max(max, Count(i));
                }
            }
            Console.WriteLine(max);
        }
        static int Count(int n)
        {
            if (n == 0) return 0;
            return Count(n >> 1) + (n & 1);
        }

    }
}