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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.ArrayList;
import java.util.Scanner;

public class Main{
	static ArrayList<Integer[]> ptList = new ArrayList<>();
	static ArrayList<Integer[][]> list = new ArrayList<>();
	static int n;
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
		n = scan.nextInt();
		createPList(n);

		int len = ptList.size();
		int a,i,j,k;

		for(i = 0; i < n; i++) {
			a = scan.nextInt();
			Integer[][] temp = new Integer[a][2];
			for(j = 0; j < a; j++) {
				temp[j][0] = scan.nextInt() - 1;
				temp[j][1] = scan.nextInt();
			}
			list.add(temp);
		}

		boolean f;
		int cnt;
		int max = Integer.MIN_VALUE;
		for(i = 0; i < len; i++) {
			f = true;
			cnt = 0;
			for(j = 0; j < n; j++) {
				if(!judge(ptList.get(i), list.get(j), j)) {
					f = false;
					break;
				}
			}
			if(f) {
				for(k = 0; k < n; k++) {
					if(ptList.get(i)[k] == 1)
						cnt++;
				}
			}else {
				cnt = 0;
			}
			if(cnt > max)
				max = cnt;
		}
		System.out.println(max);
	}
	public static void createPList(int n) {
		int pt = (int)Math.pow(2, n) - 1;

		int i,j;
		Integer[] temp;
		for(i = 0; i <= pt; i++) {
			temp = new Integer[n];
			for(j = 0; j < n; j++) {
				temp[j] = (1 & i >> j);
			}
			ptList.add(temp);
		}
	}
	public static boolean judge(Integer[] ptList, Integer[][] list, int index) {
		int i;
		boolean result = true;
		for(i = 0; i < list.length; i++) {
			int p = list[i][0];
			int v = list[i][1];
			if(ptList[index] != 1) {
				if(v == 0)
					v = 1;
				else
					v = 0;
			}
			result = ptList[p] == v;
			if(!result)
				break;
		}
		return result;
	}
}