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 PyPy3 (2.4.0) (judge verdict: Wrong Answer)

import copy
n = int(input())
HOU = []
for i in range(n):
    tmp = int(input())
    for _ in range(tmp):
        x, y = (map(int, input().split()))
        HOU.append([i, x - 1, bool(y)])

#print(HOU)
anssum = 0
print(HOU)
ans = [False] * n
for i in range(2 ** n):
    tmplist = copy.deepcopy(HOU)
    flag = True
    now = str((bin(i))[2:].zfill(n))
    #print(now)
    for j in range(n):
        ans[j] = bool(int(now[j]))
    # print(ans)
    for j in range(len(HOU)):
        if not ans[tmplist[j][0]]:
            tmplist[j][2] = not tmplist[j][2]

        if ans[tmplist[j][1]] == tmplist[j][2]:
            continue
        else:
            flag = False
            print(tmplist[j],ans[tmplist[j][1]])
            break
    if flag:
        anssum = max(anssum, sum(ans))

print(anssum)