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 Rust (1.42.0) (judge verdict: Accepted)

use proconio::input;

fn main() {
    input! {
        n: usize,
    }

    let mut testimonies: Vec<Vec<(usize, usize)>> = vec![vec![]; n];
    for i in 0..n {
        input! {
            a: usize,
        }
        for _ in 0..a {
            input! {
                x: usize,
                y: usize,
            }
            testimonies[i].push((x, y));
        }
    }

    let mut maximum = 0;
    // bit travese
    'outer: for bit in 0u64..1 << n {
        for i in 0..n {
            if bit & (1 << i) != 0 {
                for (x, y) in &testimonies[i] {
                    if !(*y == 0 && bit & (1 << (x - 1)) == 0
                        || *y == 1 && bit & (1 << (x - 1)) != 0)
                    {
                        continue 'outer;
                    }
                }
            }
        }
        //pass!
        if maximum < bit.count_ones() {
            maximum = bit.count_ones();
        }
    }

    println!("{}", maximum);
}