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 Go (1.6) (judge verdict: Wrong Answer)

package main

import (
	"bufio"
	"fmt"
	"io"
	"math"
	"os"
	"strconv"
)

func main() {
	fmt.Printf("%d\n", resolve(parseProblem(os.Stdin)))
}

func parseProblem(r io.Reader) int {
	var n int
	fmt.Fscanf(r, "%d", &n)
	sc := bufio.NewScanner(r)
	sc.Split(bufio.ScanWords)
	testimonies := []testimony{}
	for i := 0; i < n; i++ {
		testimonies = append(testimonies, parseTestimony(r))
	}
	max := uint(0)
	for i := 0; i < 1<<uint(n); i++ {
		if checkAllHornest(n, uint(i), testimonies) {
			numH := onesCount(uint(i))
			if max < numH {
				max = numH
			}
		}
	}
	return int(max)
}

func checkAllHornest(n int, i uint, testimonies []testimony) bool {
	flag := 1
	idx := 0
	for flag < 1<<uint(n) {
		if i&uint(flag) == uint(flag) {
			if i&testimonies[idx].l != i {
				return false
			}
			if i|testimonies[idx].h != i {
				return false
			}
		}
		flag <<= 1
		idx++
	}
	return true
}

func onesCount(bits uint) (num uint) {
	num = (bits >> 1) & 03333333333
	num = bits - num - ((num >> 1) & 03333333333)
	num = ((num + (num >> 3)) & 0707070707) % 077
	return
}

type testimony struct{ h, l uint }

func parseTestimony(r io.Reader) (t testimony) {
	var n int
	fmt.Scan(&n)
	sc := bufio.NewScanner(r)
	sc.Split(bufio.ScanWords)

	t.l, t.h = math.MaxUint64, 0
	for i := 0; i < n; i++ {
		sc.Scan()
		idx, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		horneset, _ := strconv.Atoi(sc.Text())
		if horneset == 0 {
			t.l ^= 1 << uint(idx-1)
		} else {
			t.h |= 1 << uint(idx-1)
		}
	}
	return
}

func resolve(n int) int {
	return n
}