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: Wrong Answer)

using System;
using System.Collections.Generic;

class Program {
    static void Main(string[] args) {

        int n = int.Parse(Console.ReadLine());

        int result = 0;

        int[] a = new int[n];
        int[,] x=new int[n,n];
        int[,] y=new int[n,n];

        for(int i = 0; i < n; i++) {
            a[i] = int.Parse(Console.ReadLine());

            for(int j = 0; j < a[i]; j++) {
                string[] xy = Console.ReadLine().Split(' ');
                x[i, j] = int.Parse(xy[0])-1;
                y[i, j] = int.Parse(xy[1]);
            }
        }

        for (int i = 0; i < Math.Pow(2 , n); i++) {
            bool[] T = new bool[n];
            int Tman=0;
            bool miniResult = true;

            int i2 = i;
            for(int j = n - 1; j >= 0; j--) {
                if (i2 > Math.Pow(2, j)) {
                    i2 -= (int)(Math.Pow(2, j));
                    T[j] = false;
                } else {
                    T[j] = true;
                    Tman++;
                }
            }

            if (Tman < result) break;


            for(int j = 0; j < n; j++) {
                if (T[j]) {
                    for(int k = 0; k < a[j]; k++) {
                        bool Tk = (y[j,k]==1);
                        if (T[x[j, k]]!=Tk) {
                            miniResult = false;
                        }
                    }
                }
            }

            if (miniResult) {
                result = Tman;
            }

        }

        Console.WriteLine(result);

    }
}