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 ConsoleApp15
{
    class Class188
    {
        
        static void Main()
        {
            int N = int.Parse(Console.ReadLine());
            var A = new List<Tuple<int, bool>>[N];
            for (int i = 0; i < N; i++) A[i] = new List<Tuple<int, bool>>();
            for(int i = 0; i < N; i++)
            {
                var a = int.Parse(Console.ReadLine());
                for(int j = 0; j < a; j++)
                {
                    var r = Console.ReadLine().Split().Select(int.Parse).ToArray();
                    A[i].Add(Tuple.Create(r[0] - 1, r[1] == 0));
                }
            }

            int ans = 0;
            for(int i = 0; i < (1 << N); i++)//unhonest:1
            {
                bool[] check = new bool[N];
                bool frag = false;
                int count = 0;
                for (int j = 0; j < N; j++)
                    if ((i & (1 << j)) > 0)
                    {
                        check[j] = true;
                    }
                    else count++;

                for(int j = 0; j < N; j++)
                {
                    if ((i & (1 << j)) > 0) continue;
                    foreach(Tuple<int,bool> t in A[j])
                    {
                        if (t.Item2)
                        {
                            if (!check[t.Item1])
                                frag = true;
                        }
                        else
                        {
                            if (check[t.Item1])
                                frag = true;
                        }
                    }
                }
                if (frag) continue;
                ans = Math.Max(ans, count);
            }
            Console.WriteLine(ans);
        }
    }
}