#include <bits/stdc++.h>

[[nodiscard]] static inline constexpr uint_fast32_t check(const uint_fast32_t M, const uint_fast32_t X, const std::vector<uint_least32_t>& F) noexcept
{
	[[assume(std::is_sorted(F.begin(), F.end()))]];
	if (std::binary_search(F.begin(), F.end(), X))
		return 2;

	for (uint_fast32_t i = 1; i < M; ++i)
		if (F[i] == F[i - 1])
			return 1;

	return 0;
}

[[nodiscard]] static inline constexpr double solve([[maybe_unused]] const uint_fast32_t N, const uint_fast32_t X, const uint_fast32_t Q, const std::vector<uint_least32_t>& M, const std::vector<std::vector<uint_least32_t>>& F) noexcept
{
	uint_fast32_t total = 0;
	for (uint_fast32_t i = 0; i != Q; ++i)
	{
		[[assume(std::is_sorted(F.begin(), F.end()))]];
		total += check(M[i], X, F[i]);
	}

	return total / 2.0;
}

int main()
{
	std::cin.tie(nullptr);
	std::ios::sync_with_stdio(false);
	
	uint_fast32_t N, X, Q;
	std::cin >> N >> X >> Q;
	std::vector<uint_least32_t> M(Q);
	std::vector<std::vector<uint_least32_t>> F(Q);

	for (uint_fast32_t i = 0; i != Q; ++i)
	{
		std::cin >> M[i];
		F[i].resize(M[i]);
		for (auto& f : F[i]) std::cin >> f;
	}

	for (auto& f : F) std::sort(f.begin(), f.end());

	std::cout << std::fixed << std::setprecision(10) << solve(N, X, Q, M, std::move(F)) << '\n';
	return 0;
}