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 static System.Math;
using System.Linq;
using System.Text;
 
class DandA {
    static void Main(string[] args) {
        int n = ReadLineInt();
        int[,] conf = new int[n, n];
        for (int i = 0;i < n;i++) {
            int a = ReadLineInt();
            int[][] xy = ReadMLineIntArray(a);
            for (int j = 0; j < a; j++) {
                conf[i, xy[j][0] - 1] = xy[j][1] == 1 ? 1 : -1;
            }
        }

        int rtn = 0;
        for (int i = 0; i < (1 << n); i++) {
            bool[] isGood = Enumerable.Range(0, n).Select(x => (i & (1 << x)) != 0).ToArray();
            bool flg = true;
            for (int j = 0; j < n; j++) {
                if (!isGood[j]) continue; 
                for (int k = 0; k < n; k++) {
                    if (conf[j, k] == 0) continue;
                    if ((conf[j, k] == 1) == isGood[k]) continue;
                        flg = false;
                        break;
                }
            }
            if (flg) {rtn = Math.Max(rtn, isGood.Count(x => x));}
        }
        Console.WriteLine(rtn);
    }
 
    static string Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ";
    static string[] strAry = new string[] {"L", "R", "U", "D"};
    static int[] intArray = new int[10];
    static List<int> intList = new List<int>();
  
    static private string ReadLineStr() {return Console.ReadLine();}
    static private int ReadLineInt() {return int.Parse(Console.ReadLine());}
    static private long ReadLineLong() {return long.Parse(Console.ReadLine());}
    static private double ReadLineDouble() {return double.Parse(Console.ReadLine());}
    static private string[] ReadLineStrArray() {return Console.ReadLine().Trim().Split();}
    static private int[] ReadLineIntArray() {return Console.ReadLine().Trim().Split().Select(a => int.Parse(a)).ToArray();}
    static private long[] ReadLineLongArray() {return Console.ReadLine().Trim().Split().Select(a => long.Parse(a)).ToArray();}
    static private double[] ReadLineDoubleArray() {return Console.ReadLine().Trim().Split().Select(a => double.Parse(a)).ToArray();}
    static private decimal[] ReadLineDecimalArray() {return Console.ReadLine().Trim().Split().Select(a => decimal.Parse(a)).ToArray();}
    static private List<int> ReadLineIntList() {return Console.ReadLine().Trim().Split().Select(a => int.Parse(a)).ToList();}
    static private List<long> ReadLineLongList() {return Console.ReadLine().Trim().Split().Select(a => long.Parse(a)).ToList();}
    static private string[][] ReadMLineStrArray(int arg) { return new int[arg].Select(_ => Console.ReadLine().Split()).ToArray();}
    static private int[][] ReadMLineIntArray(int arg) { return new int[arg].Select(_ => Console.ReadLine().Split().Select(int.Parse).ToArray()).ToArray();}
 
    static private bool IsPrime(int num) {
        if (num < 2) return false;
        if (num == 2) return true;
        else if (num % 2 == 0) return false;
        double sqrtNum = Math.Sqrt(num);
        for (int i = 3; i <= sqrtNum; i += 2) {
            if (num % i == 0) return false;
        }
        return true;
    }
  
    static private string IntToNString(int x, int n) {
        var nstring = "";
        var numbers = new string[] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };
        int r = 1;
        int q = x;
        while (q > 0) {
            r = q % n;
            nstring += numbers[r];
            q = q / n;
        }
        return string.Join("",nstring.Reverse());
     }
}