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# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;

namespace C
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            var G = new int[15, 15];
            for (int i = 0; i < 15; i++) { for (int j = 0; j < 15; j++) { G[i, j] = -1; } }
            for (int i = 0; i < n; i++)
            {
                int m = int.Parse(Console.ReadLine());
                for (int j = 0; j < m; j++)
                {
                    string[] In = Console.ReadLine().Split(' ');
                    int a = int.Parse(In[0]);
                    int x = int.Parse(In[1]);
                    a--;
                    G[i, a] = x;
                }
            }
            int ans = 0;
            //参加者各々が正しい正しくないの全通りを試す
            for (int i = 0; i < (1 << n); i++)//1<<0=1 1<<1=2 1<<2=4　なので1<<nはn+1桁の2進数で表せる最大の数
            {
                var d = new int[n];
                for (int j = 0; j < n; j++)
                {
                    if (((i >> j) & 1) == 1) { d[j] = 1; }//iのjビット目が１か
                }
                bool ok = true;
                for (int j = 0; j < n; j++)
                {
                    if (d[j] == 1)
                    {
                        for (int k = 0; k < n; k++)
                        {
                            if (G[j, k] == -1) continue;
                            if (G[j, k] != d[k]) ok = false;
                        }
                    }
                }
                if (ok) ans = (int)Math.Max(ans, CountBit1(i));
            }
            Console.WriteLine(ans);
        }
        public static int CountBit1(int n)
        {
            string str="";
            while (n != 0)
            {
                str += n % 2;
                n /= 2;
            }
            int cnt = 0;
            foreach(var s in str)
            {
                if (s == '1') cnt++;
            }
            return cnt;
        }
    }
}