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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
#define rep(i,n) for (ll i = 0; i < (n); ++i)
using namespace std;
using ll = long long;
using ull = long long unsigned;
using P = pair<int,int>;
const int INF=1001001;
const int NMAX=8;


int main()
{
	int n;
	cin>>n;
	int x[20][20];
	int y[20][20];
	int a[20];
	rep(i,n){
		cin>>a[i];
		rep(j,a[i]){
			cin>>x[i][j];
			cin>>y[i][j];
				}
	}
	int ans=0;
	rep(i,1<<n){
		int cnt=0;
		bool ok=true;
		rep(j,n){
			if (i & (1<<j)){
				cout<<j<<endl;
				cnt++;
				rep(k,a[j]){
					if (y[j][k]==0){
						if(i and (1<<i)){
							ok=false;
						}
					}
					if (y[j][k]==1){
						if(!(i and (1<<i))){
							ok=false;
						}
					}
				}

			}

		}
	//	cout<<i<<'i'<<(ok==true)<<endl;


		if (ok==true){
			ans=max(ans,cnt);
		}


	}
	cout<<ans;



}