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 Kotlin (1.3.71) (judge verdict: Wrong Answer)

fun main(args: Array<String>) {
    val n = readLine()!!.toInt()

    val s = arrayOfNulls<List<Pair<Int, Int>>>(n)
    repeat(n) {
        val a = readLine()!!.toInt()
        val lst = mutableListOf<Pair<Int, Int>>()
        repeat(a) {
            val (x, y) = readLine()!!.split(' ').map { it.toInt() }
            lst.add(x-1 to y)
        }
        s[it] = lst
    }

    var ans = 0

    fun chk(onoff: String) {
        val oncnt = onoff.count { it == '1' }
        if (oncnt <= ans) return
        var success = true
        val state = IntArray(n) { -1 }
        var changed = true
        while (changed && success) {
            changed = false
            for (i in onoff.indices) {
                if (onoff[i] == '1' || state[i] == 1) {
                    state[i] = 1
                    val shogen = s[i]
                    shogen!!.forEach {
                        val target = it.first
                        if (state[target] == -1) {
                            state[target] = it.second
                            if (it.second == 1) changed = true
                        } else {
                            success = success && (state[target] == it.second)
                        }
                    }
                }
            }
        }
        if (success) {
            ans = state.count { it == 1 }
        }
    }

    val max = Math.pow(2.0, n.toDouble()).toInt() -1
    for (i in 0..max) {
        val bStr = String.format("%${n}s", Integer.toBinaryString(i)).replace(" ", "0")
        chk(bStr)
    }

    println(ans)
}