#include <bits/stdc++.h>

[[nodiscard]] static inline uint_fast32_t check(const uint_fast32_t M, const uint_fast32_t X, const std::vector<uint_least32_t>& F) noexcept
{
	std::unordered_map<uint_least32_t, uint_least32_t> count_of;
	count_of.reserve(M);
	for (const auto& f : F) ++count_of[f];

	if (count_of.contains(X))
		return 2;

	for (const auto& [key, count] : count_of)
		if (count >= 2)
			return 1;

	return 0;
}

[[nodiscard]] static inline 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)
		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;
	}

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