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)

/*2019/10/19 */
/*template*/
#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include<string.h>
#define MOD 1000000007
#define MIN 999999999
#define MAX -999999999
typedef long long int ll;
typedef unsigned long long int ull;
void llswap(ll *x,ll *y){ll tmp;tmp=*x;*x=*y;*y=tmp;}
void swap(int *x,int *y){int tmp;tmp=*x;*x=*y;*y=tmp;}
int rmax(int x,int y){return x>y?x:y;}
int rmin(int x,int y){return x>y?y:x;}
ll llrmax(ll x,ll y){return x>y?x:y;}
ll llrmin(ll x,ll y){return x>y?y:x;}
int asc(const void *a,const void *b){if(*(int*)a < *(int*)b)return -1;else if(*(int*)a == *(int*)b)return 0;else return 1;}
int desc(const void *a,const void *b){if(*(int*)a < *(int*)b)return 1;else if(*(int*)a == *(int*)b)return 0;else return -1;}
int llasc(const void *a,const void *b){if(*(ll*)a < *(ll*)b)return -1;else if(*(ll*)a == *(ll*)b)return 0;else return 1;}
int lldesc(const void *a,const void *b){if(*(ll*)a < *(ll*)b)return 1;else if(*(ll*)a == *(ll*)b)return 0;else return -1;}
int gcd(int x,int y){if(y==0)return x;return gcd(y,x%y);}
 
//int asc_t(const void *a,const void *b){if(((pair_t*)a)->d < ((pair_t*)b)->d)return -1;else if(((pair_t*)a)->d == ((pair_t*)b)->d)return 0;else return 1;}
//int asc_t(const void *a,const void *b){if(((pair_t*)a)->d < ((pair_t*)b)->d)return 1;else if(((pair_t*)a)->d == ((pair_t*)b)->d)return 0;else return -1;}
double to_deg(double r) {return r * 180.0 / (atan(1.0) * 4.0);}

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

    int list[100][100]={{}};
    
    for(int i=1;i<=n;i++){
        scanf("%d",&a);
        for(int j=0;j<a;j++){
            scanf("%d %d",&x,&y);
            if(y==1)list[i][x]=1;
            else list[i][x]=-1;
        }
    }
    
    int cnt=0,max=-1;
    int tmp;
    for(int i=1;i<=n;i++){
        cnt=1;
        for(int j=1;j<=n;j++){
            if(i==j)continue;
            if(list[i][j]==-1)continue;
            for(int k=1;k<=n;k++){
                if(list[j][k]==-1&&i==k){
                    cnt=0;
                    goto END;
                }
                if(list[j][k]==1)cnt++;
            }
        }
        END:
        //printf("i:%d cnt:%d\n",i,cnt);
        if(cnt>max)max=cnt;
    }
    printf("%d\n",max);
    return 0;
}