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 AtCoder_solve
{
    class Program
    {
        public const ulong mod = 1000000007;

        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            int[][] say = new int[n+1][];
            long ans = 0;

            for (int i = 0; i < n; i++)
            {
                int a= int.Parse(Console.ReadLine());
                say[i + 1] = new int[n+1];
                for (int j = 0; j < a; j++)
                {
                    int[] data = Console.ReadLine().Split().Select(int.Parse).ToArray();
                    int x = data[0];
                    int y = data[1];
                    say[i + 1][x] = y+1;
                }
            }
            
            for(int k = 0; k < (1 << n); k++)
            {
                int[] katei = new int[n + 1];
                bool judge = true;
                for(int l = 1; l <= n; l++)
                {
                    if (((k >> l - 1) & 1) == 1) katei[l] = 2;
                    else katei[l] = 1;
                }
                for(int m = 1; m <= n; m++)
                {
                    if (katei[m]==2)
                    {
                        for(int ii=1;ii<=n;ii++)
                        {
                            if (say[m][ii] != 0&&katei[ii]!=say[m][ii])
                            {
                                judge = false;
                                break;
                            }
                        }
                    }
                    if (!judge) break;
                }
                if (judge)
                {
                    int max = 0;
                    foreach (var chara in katei)
                    {
                        if (chara == 2) max++;
                        ans = Math.Max(ans, max);
                    }
                }
            }

            Console.WriteLine(ans);



            

        }

        static public long Input()
        {
            return long.Parse(Console.ReadLine());
        }

        static public string[] Input2()
        {
            return Console.ReadLine().Split();
        }
        
        static public long[] Input3()
        {
            string[] data = Console.ReadLine().Split();
            long[] res = new long[data.LongLength];
            for(long i = 0; i < data.LongLength; i++)
            {
                res[i] = long.Parse(data[i]);
            }
            return res;
        }
        public static long Choose(long n, long a)
        {
            long x = 1;
            long y = 1;
            for (long i = 0; i < a; i++)
            {
                x *= n - i;
                y *= i + 1;
            }
            return x / y;
        }

        public static long Gcd(long a, long b)
        {
            long x = Math.Max(a, b);
            long y = Math.Min(a, b);
            if (x % y == 0) return y;
            else return Gcd(y, x % y);
        }

        
       
    }
}