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;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    static class CHonestOrUnkind2
    {
        static void Main(string[] args)
        {
            var n = int.Parse(Console.ReadLine());
            var list = new List<List<Tuple<int, int>>>();

            for (int i = 0; i < n; i++)
            {
                var a = int.Parse(Console.ReadLine());
                list.Add(new List<Tuple<int, int>>());
                for (int j = 0; j < a; j++)
                {
                    var xy = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToList();                    
                    list[i].Add(Tuple.Create(xy[0]- 1, xy[1]));
                }
            }

            int max = 0;
            for (int i = 0; i < n; i++)
            {
                max = Math.Max(max, HonestOrUnkind(n, i, list));
            }

            Console.WriteLine(max);
            Console.ReadLine();
        }

        static int HonestOrUnkind(int memberCount, int num, List<List<Tuple<int, int>>> list)
        {            
            var xxx = new List<int>();
            for (int i = 0; i < memberCount; i++)
            {
                xxx.Add(0);
            }

            // num is temp Honest.
            xxx[num] = 1;
            foreach (var numItem in list[num])
            {
                xxx[numItem.Item1] = numItem.Item2;
            }

            for (int i = 0; i < list.Count; i++)
            {
                // Myself skip.
                if (i == num) continue;
                // Temp unkind from myself skip.
                if (xxx[i] == 0) continue;

                foreach (var tempHonest in list[i])
                {
                    if (xxx[tempHonest.Item1] != tempHonest.Item2) return 0;
                }
            }

            return xxx.Sum();
        }
    }
}