#include <fstream>
#define MAX 1000

using namespace std;

short n,ans;
short s[1000][1000];
bool f[MAX][1000];
short deep[MAX];

void input();
void output(const short x);
bool pd(const short x);
void bps();

int main()
{
	input();
	bps();
}

void input()
{
	ifstream fin("t3.in");
	fin>>n;
	for (short i=0; i<n; i++)
	{
		fin>>f[0][i];
		while ((fin.get()!='\n')&&(fin.eof()!=true))
			fin>>s[i][++s[i][0]];
	}
}

void output(const short x)
{
	ofstream fout("t3.out");
	fout<<x<<endl;
	fout.close();
	exit(0);
}

bool pd(const short x)
{
	for (short i=0; i<n; i++)
		if (f[x][i]==false)
			return false;
	return true;
}

void bps()
{
	short j=0,k=1,i,o;
	do{
		for (i=0; i<n; i++)
		{
			for (o=0; o<n; f[k][o]=f[j][o++]);
			for (o=1; o<=s[i][0]; f[k][s[i][o]]=!(f[k][s[i][o++]]));
			if (pd(k))
				output(deep[j]+1);
			deep[k]=deep[j]+1;
		}
	} while (k<=MAX);
}