# -*- coding: utf-8 -*-
import sys
import math
import os
import itertools
import string
import heapq
import _collections
from collections import Counter
from collections import defaultdict
from collections import deque
from functools import lru_cache
import bisect
import re
import queue
import decimal


class Scanner():
    @staticmethod
    def int():
        return int(sys.stdin.readline().rstrip())

    @staticmethod
    def string():
        return sys.stdin.readline().rstrip()

    @staticmethod
    def map_int():
        return [int(x) for x in Scanner.string().split()]

    @staticmethod
    def string_list(n):
        return [Scanner.string() for i in range(n)]

    @staticmethod
    def int_list_list(n):
        return [Scanner.map_int() for i in range(n)]

    @staticmethod
    def int_cols_list(n):
        return [Scanner.int() for i in range(n)]


class Math():
    @staticmethod
    def gcd(a, b):
        if b == 0:
            return a
        return Math.gcd(b, a % b)

    @staticmethod
    def lcm(a, b):
        return (a * b) // Math.gcd(a, b)

    @staticmethod
    def divisor(n):
        res = []
        i = 1
        for i in range(1, int(n ** 0.5) + 1):
            if n % i == 0:
                res.append(i)
                if i != n // i:
                    res.append(n // i)
        return res

    @staticmethod
    def round_up(a, b):
        return -(-a // b)

    @staticmethod
    def is_prime(n):
        if n < 2:
            return False
        if n == 2:
            return True
        if n % 2 == 0:
            return False
        d = int(n ** 0.5) + 1
        for i in range(3, d + 1, 2):
            if n % i == 0:
                return False
        return True

    @staticmethod
    def fact(N):
        res = {}
        tmp = N
        for i in range(2, int(N ** 0.5 + 1) + 1):
            cnt = 0
            while tmp % i == 0:
                cnt += 1
                tmp //= i
            if cnt > 0:
                res[i] = cnt
        if tmp != 1:
            res[tmp] = 1
        if res == {}:
            res[N] = 1
        return res


def pop_count(x):
    x = x - ((x >> 1) & 0x5555555555555555)
    x = (x & 0x3333333333333333) + ((x >> 2) & 0x3333333333333333)
    x = (x + (x >> 4)) & 0x0f0f0f0f0f0f0f0f
    x = x + (x >> 8)
    x = x + (x >> 16)
    x = x + (x >> 32)
    return x & 0x0000007f


MOD = int(1e09) + 7
INF = int(1e15)


def solve():
    N = Scanner.int()
    A = [[-1 for _ in range(N)] for _ in range(N)]
    for i in range(N):
        a = Scanner.int()
        for _ in range(a):
            x, y = Scanner.map_int()
            x -= 1
            A[i][x] = y
    ans = 0
    for i in range(1 << N):
        truth = [False for _ in range(N)]
        for j in range(N):
            if i >> j & 1:
                truth[j] = True
        isOK = True
        for j in range(N):
            if not truth[j]:
                continue
            for k in range(N):
                if j == k:
                    continue
                if A[j][k] == 0 and truth[k]:
                    isOK = False
                if A[j][k] == 1 and not truth[k]:
                    isOK = False
        if isOK:
            ans = max(sum(truth), ans)
    print(ans)


def main():
    # sys.stdin = open("sample.txt")
    # T = Scanner.int()
    # for _ in range(T):
    #     solve()
    # print('YNeos'[not solve()::2])
    solve()


if __name__ == "__main__":
    main()


Measured memory_bytes: 10724