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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;
import java.io.BufferedReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author MaxHeap
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        CHonestOrUnkind2 solver = new CHonestOrUnkind2();
        solver.solve(1, in, out);
        out.close();
    }

    static class CHonestOrUnkind2 {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int n = in.nextInt();
            CHonestOrUnkind2.Person[] persons = new CHonestOrUnkind2.Person[n];
            for (int i = 0; i < n; ++i) {
                int a = in.nextInt();
                persons[i] = new CHonestOrUnkind2.Person();
                for (int j = 0; j < a; ++j) {
                    persons[i].testimonies.add(new CHonestOrUnkind2.Testimony(in.nextInt() - 1, in.nextInt()));
                }
            }
            int best = 0;
            for (int i = 0; i < (1 << n); ++i) {
                boolean contradiction = false;
                outer:
                for (int j = 0; j < n; ++j) {
                    if ((i & (1 << j)) > 0) {
                        List<CHonestOrUnkind2.Testimony> test = persons[j].testimonies;
                        for (CHonestOrUnkind2.Testimony testimony : test) {
                            if ((i & (1 << testimony.x)) > 0) {
                                if (testimony.y == 0) {
                                    contradiction = true;
                                    break outer;
                                }
                            } else {
                                if (testimony.y == 1) {
                                    contradiction = true;
                                    break outer;
                                }
                            }
                        }
                    }
                }
                if (!contradiction) {
                    best = Math.max(best, Integer.bitCount(i));
                }
            }
            out.println(best);
        }

        static class Testimony {
            int x;
            int y;

            public Testimony(int x, int y) {
                this.x = x;
                this.y = y;
            }

            public String toString() {
                return "Testimony{" +
                    "x=" + x +
                    ", y=" + y +
                    '}';
            }

        }

        static class Person {
            List<CHonestOrUnkind2.Testimony> testimonies = new ArrayList<>();

        }

    }

    static class InputReader {
        private StringTokenizer st;
        private BufferedReader reader;

        public InputReader(InputStream is) {
            st = null;
            reader = new BufferedReader(new InputStreamReader(new BufferedInputStream(is, 1 << 18)));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    return null;
                }
            }
            return st.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }
}