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())
#
# ans = []
# for i in range(N):
#     A = int(input())
#     for j in range(A):
#         ans.append(list(map(int, input().split())))
#
# print(ans)

print(bin(1 << 15))
print(1 << 15)
print(2**15)
n= int(input())
shogens = []
for i in range(n):
    a = int(input())
    shogens.append([])
    for j in range(a):
        x, y = map(int, input().split())
        x -= 1
        shogens[i].append((x, y))
print(shogens)

# def is_honest(i, j):
#     return (i >> j) % 2 == 1
#
# def honest_cnt(i):
#     ans = 0
#     for j in range(n):
#         ans += is_honest(i, j)
#     return ans
# ans = 0
#
# for i in range(1 << n):
#     ok = True
#     print(bin(i))
#     for j in range(n):
#         if not is_honest(i, j):continue
#         for (x, y) in shogens[j]:
#             if y == 0 and is_honest(i, x):ok = False
#             if y == 1 and not is_honest(i, x):ok = False
#
#     if ok:
#         ans = max(ans, honest_cnt(i))
#
# print("ans", ans)

lists = {i : 0 for i in range(1 << 15)}
for i in range(1 << 15):
    count = 0
    for j in range(n):
        if (i >> j) & 1:
            for x, y in shogens[j]:
                if y == 0 and (i >> x) & 1: count -= 1
                if y == 1 and not (i >> x) & 1: count -= 1
    if count == 0:
        ans = 0
        for k in range(n):
            ans += (i >> k) % 2
        lists[i] = ans

print(max(lists.values()))
# print(0 >> 0)