#include <bits/stdc++.h>

[[nodiscard]] static inline constexpr std::vector<uint_least32_t> prepare(std::vector<uint_least32_t>&& F) noexcept
{
	std::sort(F.begin(), F.end());
	return std::move(F);
}

[[nodiscard]] static inline constexpr uint_fast32_t solve(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 - 1] == F[i]) return 1;

	return 0;
}

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

	uint_fast32_t total = 0;
	for (uint_fast32_t i = 0; i != Q; ++i)
	{
		uint_fast32_t M;
		std::cin >> M;
		std::vector<uint_least32_t> F(M);
		for (auto& f : F) std::cin >> f;

		total += solve(M, X, prepare(std::move(F)));
	}

	std::cout << std::fixed << std::setprecision(10) << total / 2.0 << '\n';
	return 0;
}