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#include <iostream>
#include <string>
#include <cctype>

#include <string.h>

#define SIZE_OF_ARRAY(x) (sizeof(x) / sizeof(*(x)))

#ifndef _MSC_VER
#define __int64 long long
#endif

typedef unsigned short uint16;
typedef unsigned int uint;
typedef unsigned __int64 uint64;

static char get_char_buffer[4 * 1024];
static std::size_t get_char_buffer_i = SIZE_OF_ARRAY(get_char_buffer);
static std::size_t get_char_buffer_n = SIZE_OF_ARRAY(get_char_buffer);

static char get_char_prefix = 0;
static char get_char_result = 0;

int get_char()
{
	get_char_result = 0;

	if (get_char_prefix)
	{
		get_char_result = get_char_prefix;

		get_char_prefix = 0;
	}
	else if (get_char_buffer_n == 0)
	{
		get_char_result = std::char_traits<char>::eof();
	}
	else if (get_char_buffer_i < get_char_buffer_n)
	{
		get_char_result = get_char_buffer[get_char_buffer_i++];
	}
	else
	{
		std::cin.read(get_char_buffer, SIZE_OF_ARRAY(get_char_buffer));

		get_char_buffer_i = 0;
		get_char_buffer_n = std::cin.gcount();

		return get_char();
	}

	return get_char_result;
}

void unget_char()
{
	get_char_prefix = get_char_result;
}

uint get_uint()
{
	int c;
	while (isspace(c = get_char()));

	uint value = (c - '0');

	while (isdigit(c = get_char()))
	{
		value = (10 * value) + (c - '0');
	}

	return value;
}

uint l[502];
uint16 h[502][1002];

uint16 s[1002];
int t[1002];

int main()
{
	std::ios_base::sync_with_stdio(false);
	std::cin.tie(0);

	uint n = get_uint();
	uint m = get_uint();

	for (uint i = 1; i <= n; ++i)
	{
		l[i] = get_uint();

		for (uint j = 0; j < l[i]; ++j)
		{
			h[i][j] = get_uint();
		}
	}

	for (uint i = 0; i < m; ++i)
	{
		s[i] = get_uint();
	}

	t[0] = -1;

	for (uint i = 1; i <= m; i++)
	{
		int pos = t[i - 1];

		while (pos != -1 && s[pos] != s[i - 1])
		{
			pos = t[pos];
		}

		t[i] = pos + 1;
	}

	uint max_size = 60000000 / sizeof(uint16);

	uint16 *curr = new uint16[max_size];
	uint16 *next = new uint16[max_size];

	uint curr_size = 1;
	curr[0] = 1;

	uint time = 1;

	while (curr_size < max_size)
	{
		uint sp = 0;
		uint kp = 0;

		while (sp < curr_size)
		{
			while (kp != -1 && (kp == m || s[kp] != curr[sp]))
			{
				kp = t[kp];
			}

			kp++;
			sp++;

			if (kp == m)
			{
				std::cout << time << '\n';

				return 0;
			}
		}

		uint next_size = 0;

		for (uint i = 0; i < curr_size; ++i)
		{
			if (next_size + l[curr[i]] >= max_size)
			{
				next_size = max_size;

				break;
			}

			memcpy(next + next_size, h[curr[i]], l[curr[i]] * sizeof(uint16));

			next_size += l[curr[i]];
		}

		std::swap(curr, next); curr_size = next_size;

		++time;
	}

	std::cout << "-1\n";

	return 0;
}