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: Wrong Answer)

#include<stdio.h>
int main(){
  int n,i,j,l,m;
  scanf("%d",&n);
  int a[n+1];
  int x[n+1][n],y[n+1][n];
  int z[n+1];
  int count;
  for(i=1;i<n+1;i++)
    z[i]=0;
  for(i=1;i<n+1;i++){
    scanf("%d",&a[i]);
    for(j=1;j<a[i]+1;j++)
      scanf("%d%d",&x[i][j],&y[i][j]);
  }
  count=0;
  if(n==1)
    printf("1\n");
  else if(n==2){
    if(a[1]==0||a[2]==0)
      printf("2\n");
    else{
      if(y[1][1]==y[2][1])
	printf("1\n");
    }
  }
  else{
    for(i=1;i<n+1;i++)
      for(j=1;j<a[i]+1;j++){
	if(y[i][j]==0)
	  z[x[i][j]]++;
      }
    for(i=1;i<n+1;i++)
      if(z[i]!=0)
	count++;
    printf("%d\n",n-count);
  }
  return 0;
}