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 C (GCC 5.4.1) (judge verdict: Runtime Error)

#include <stdio.h>
#include <stdbool.h>

int a[20];
int x[20][20];
int y[20][20];

int bit_sum(int bit)
{
	if(bit==0){
		return 0;
	}

	return (bit >> 1) + (bit & 1);
}

int main()
{
	int n;
	scanf("%d",&n);

	int a[n];
	for(int i=1;i<=n;i++){
		scanf("%d",&a[i]);
		for(int j=1;j<=n;j++){
			scanf("%d",&x[i][j]);
			scanf("%d",&y[i][j]);				
		}
	}

	int bit;
	int ans = 0;
	for(bit=1;bit< (1<< n);bit++){
		bool ok = true;
		for(int i=1;i<=n;i++){
			if(!( bit & (1 << i-1))){
				continue;
			}
			for(int j=1;j<=a[i];j++){
				if(((bit >> (x[i][j]-1)) & 1)^y[i][j]){
					ok = false;
				}
			}
		}
		if(ok){
			if(ans < bit_sum(bit)){
				ans = bit_sum(bit);
			}
		}
	}
	
	printf("%d",ans);
	
	return 0;
}