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.Text;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using static System.Console;
using static System.Math;

namespace AtCoder
{
    public class Program
    {
        public static void Main(string[] args)
        {
            new Program().Solve(new ConsoleInput(Console.In, ' '));
        }

        public void Solve(ConsoleInput cin)
        {
            var N = cin.ReadInt;
            var data = new List<Tuple<int, int>[]>();
            var A = new int[N];
            for (int i = 0; i < N; i++)
            {
                A[i] = cin.ReadInt;
                var d = new Tuple<int, int>[A[i]];
                for (int j = 0; j < A[i]; j++)
                {
                    var x = cin.ReadInt;
                    var y = cin.ReadInt;
                    d[j] = new Tuple<int, int>(x, y);
                }
                data.Add(d);
            }

            var ans = 0;
            var boolArray = GetBoolArray(N);

            for (int k = 0; k < Pow(2, N); k++)
            {
                var testData = boolArray[k];
                var flag = true;
                for (int i = 0; i < N; i++)
                {
                    if (!testData[i]) continue;
                    for (int j = 0; j < A[i]; j++)
                    {
                        var dd = data[i][j];
                        if ((testData[dd.Item1 - 1] && dd.Item2 != 1) || (!testData[dd.Item1 - 1] && dd.Item2 != 0))
                        {
                            flag = false;
                            break;
                        }
                    }
                    if (!flag)
                    {
                        break;
                    }
                }
                if (flag)
                {
                    ans = Max(ans, testData.Count(b => b));
                }
            }

            Console.WriteLine(ans);
        }

        static bool[][] GetBoolArray(int n)
        {
            List<bool[]> matrix = new List<bool[]>();
            double count = Math.Pow(2, n);
            for (int i = 0; i < count; i++)
            {
                string str = Convert.ToString(i, 2).PadLeft(n, '0');
                bool[] boolArr = str.Select((x) => x == '1').ToArray();

                matrix.Add(boolArr);
            }

            bool[][] arr = matrix.ToArray();

            return arr;
        }
    }

    public class ConsoleInput
    {
        private readonly System.IO.TextReader _stream;
        private char _separator = ' ';
        private Queue<string> inputStream;
        public ConsoleInput(System.IO.TextReader stream, char separator = ' ')
        {
            this._separator = separator;
            this._stream = stream;
            inputStream = new Queue<string>();
        }
        public string Read
        {
            get
            {
                if (inputStream.Count != 0) return inputStream.Dequeue();
                string[] tmp = _stream.ReadLine().Split(_separator);
                for (int i = 0; i < tmp.Length; ++i)
                    inputStream.Enqueue(tmp[i]);
                return inputStream.Dequeue();
            }
        }
        public string ReadLine { get { return _stream.ReadLine(); }}
        public int ReadInt { get { return int.Parse(Read); }}
        public long ReadLong { get { return long.Parse(Read); }}
        public double ReadDouble { get { return double.Parse(Read); }}
        public string[] ReadStrArray(long N) { var ret = new string[N]; for (long i = 0; i < N; ++i) ret[i] = Read; return ret;}
        public int[] ReadIntArray(long N) { var ret = new int[N]; for (long i = 0; i < N; ++i) ret[i] = ReadInt; return ret;}
        public long[] ReadLongArray(long N) { var ret = new long[N]; for (long i = 0; i < N; ++i) ret[i] = ReadLong; return ret;}
    }
}