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 Python (3.4.3) (judge verdict: Wrong Answer)

n = int(input())
total = list()
good = list()
bad = list()
for i in range(1,n+1):
    t = int(input())
    A = list()
    for index in range(1,t+1):
        _input = input().split(" ")
        x = int(_input[0])
        y = int(_input[1])
        A.append((x, y))
    total.append(A)

for person in total:
    good_person = list()
    bad_person = list()
    x = [x[0] for x in person]
    y = [y[1] for y in person]
    for index, a in enumerate(y):
        if a == 1:
            # good
            good_person.append(x[index])
        else:
            bad_person.append(x[index])
    #     print("check good 1",good_person)
    #     print("check bad 1", bad_person)
    # print("check good 2",good_person)
    # print("check bad 2", bad_person)
    good.append(good_person)
    bad.append(bad_person)

print(len(good) - len(bad))