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;

class Program
{
    static void Main()
    {
        Console.WriteLine(Solve());
        //Solve();
        return;
    }

    public static string Solve()
    {
        int ans = 0;
        int N = ReadInt();
        List<List<int>> g = new List<List<int>>();
        for (int i = 0; i < N; i++)
        {
            int A = ReadInt();
            List<int> xy = new List<int>();
            for (int j = 0; j < A; j++)
            {
                int[] inputs = ReadInts();
                xy.Add(inputs[0]);
                xy.Add(inputs[1]);
            }
            g.Add(xy);
        }

        bool f = false;
        int tm;
        int[] torf = new int[N];
        for (int i = 0; i < Math.Pow(2, N); i++)
        {
            int n = i;
            tm = 0;
            for (int j = 0; j < N; j++)
            {
                torf[j] = n % 2;
                if (torf[j] == 1) tm += 1;
                n /= 2;
            }
            for (int j = 0; j < N; j++)
            {
                if (torf[j] == 1)
                {
                    for (int k = 0; k < g[j].Count / 2; k++)
                    {
                        int x = g[j][k * 2] - 1;
                        int y = g[j][k * 2 + 1];
                        if (torf[x] != y)
                        {
                            f = true;
                        }
                    }
                }
            }
            if (!f)
            {
                ans = Math.Max(ans, tm);
            }
            f = false;
        }

        return ans.ToString();
    }

    private static string Read() { return Console.ReadLine(); }
    private static int ReadInt() { return int.Parse(Read()); }
    private static long ReadLong() { return long.Parse(Read()); }
    private static double ReadDouble() { return double.Parse(Read()); }
    private static int[] ReadInts() { return Array.ConvertAll(Read().Split(), int.Parse); }
    private static long[] ReadLongs() { return Array.ConvertAll(Read().Split(), long.Parse); }
    private static double[] ReadDoubles() { return Array.ConvertAll(Read().Split(), double.Parse); }
}