using System;
using System.Collections.Generic;
using System.Linq;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            var personCount = int.Parse(Console.ReadLine());

            var persons = new List<Person>();

            for (int i = 1; i <= personCount; i++)
            {
                var testCount = int.Parse(Console.ReadLine());

                var tests = new List<Test>();

                for (int ti = 0; ti < testCount; ti++)
                {
                    var vals = Console.ReadLine().Split(' ');
                    var target = int.Parse(vals[0]);
                    var isHonest = int.Parse(vals[1]) == 1;
                    tests.Add(new Test(target, isHonest));
                }

                persons.Add(new Person(i, tests.ToArray()));
            }

            //unkind = 0人
            if (IsAllowed(persons, new int[0]))
            {
                Console.WriteLine(personCount);
                return;
            }

            for (int unkindCount = 1; unkindCount <= personCount; unkindCount++)
            {
                foreach (var combi in EnumerateCombination(Enumerable.Range(1, personCount), unkindCount))
                {
                    if (IsAllowed(persons, combi))
                    {
                        Console.WriteLine(personCount - unkindCount);
                        return;
                    }
                }
            }

            Console.WriteLine(0);
        }


        private static bool IsAllowed(IEnumerable<Person> all, int[] unkindNumbers)
        {
            var kateiList = all.Select(p => new PersonIf(p, !unkindNumbers.Contains(p.Number))).ToArray();

            return IsAllCollect(kateiList);
        }

        private static bool IsAllCollect(PersonIf[] kateiList)
        {
            foreach (var katei in kateiList)
            {
                if (!katei.MaybeHonest) continue;

                foreach (var test in katei.Person.Tests)
                {
                    var target = kateiList.Single(k => k.Person.Number == test.Number);
                    if (test.IsHonest)
                    {
                        if (target.MaybeHonest) continue;

                        return false;
                    }
                    else
                    {
                        if (target.MaybeHonest) return false;
                    }
                }
            }

            return true;
        }


        private static IEnumerable<int[]> EnumerateCombination(IEnumerable<int> all, int count)
        {
            if (count == 0)
            {
                yield break;
            }
            if (count == 1)
            {
                foreach (var n in all)
                {
                    yield return new[] { n };
                }
                yield break;
            }

            foreach (var n in all)
            {
                var leftside = new int[] { n };

                var unused = all.SkipWhile(e => e != n).Skip(1).ToList();

                foreach (var rightside in EnumerateCombination(unused, count - 1))
                {
                    yield return leftside.Concat(rightside).ToArray();
                }
            }

        }
    }

    class PersonIf
    {
        public Person Person { get; }

        public bool MaybeHonest { get; set; }

        public PersonIf(Person person, bool maybeHonest)
        {
            this.Person = person;
            this.MaybeHonest = maybeHonest;
        }
    }

    class Person
    {
        public int Number { get; }
        public Test[] Tests { get; }

        public Person(int number, Test[] tests)
        {
            if (number < 1 || 15 < number) throw new ArgumentOutOfRangeException(nameof(number));

            this.Number = number;
            this.Tests = tests;
        }
    }

    class Test
    {

        public int Number { get; }
        public bool IsHonest { get; }
        public Test(int number, bool isHonest)
        {
            this.Number = number;
            this.IsHonest = isHonest;
        }
    }
}


Measured memory_bytes: 17852