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.Windows;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Atcoder
{
    public class Program
    {
        static void Main(string[] args)
        {
            var n = Read().ToInt();
            var res = new List<Tuple<int, Tuple<int, int>>>();
            for (int i = 0; i < n; i++)
            {
                var a = Read().ToInt();
                for (int j = 0; j < a; j++)
                {
                    var r = ReadSplit();
                    res.Add(new Tuple<int, Tuple<int, int>>(i, new Tuple<int, int>(r[0].ToInt() - 1, r[1].ToInt())));
                }
            }

            var max = 0;
            var count = 0;
            for (int i = 0; i < 1 << n; i++)
            {
                bool hasError = false;
                count = 0;
                var tmp = new bool[n];

                for (int j = 0; j < n; j++)
                {
                    if ((i >> j & 1) == 1)
                    {
                        tmp[j] = true;
                        count++;
                    }
                    else
                    {
                        tmp[j] = false;
                    }
                }
                for (int j = 0; j < n; j++)
                {
                    if (!tmp[j]) continue;
                    foreach (var item in res.Where(x => x.Item1 == j))
                    {
                        var cur = tmp[item.Item2.Item1];
                        var jud = item.Item2.Item2;
                        
                        if (cur != (jud == 1))
                        {
                            hasError = true;
                            count = 0;
                            break;
                        }
                     }
                }
                if (!hasError)
                {
                    max = Math.Max(max, count);
                }
            }
            WriteRead(max);
        }

        public static string Read()
        {
            return Console.ReadLine();
        }

        public static string[] ReadSplit()
        {
            return Console.ReadLine().Split(' ');
        }

        public static void WriteRead(object str)
        {
            Console.WriteLine(str);
            Read();
        }

        public static void Write(object str)
        {
            Console.WriteLine(str);
        }
    }
}


public static class Extentions
{
    public static int ToInt(this object obj)
    {
        return int.Parse(obj.ToString());
    }

    public static decimal ToDecimal(this object obj)
    {
        return decimal.Parse(obj.ToString());
    }

    public static double ToDouble(this object obj)
    {
        return double.Parse(obj.ToString());
    }

    public static T2 GetValueZero<T1, T2>(this Dictionary<T1, T2> d, T1 key) where T2 : struct
    {
        T2 value;
        if (d.TryGetValue(key, out value))


        {
            return value;
        }
        return new T2();
    }
}