#include <bits/stdc++.h>

[[nodiscard]] static inline uint_fast32_t prepare([[maybe_unused]] const uint_fast32_t N, const uint_fast32_t M, const std::vector<uint_least32_t>& S, const std::vector<uint_least32_t>& T) noexcept
{
	[[assume(std::is_sorted(S.begin(), S.end()))]];
	std::multiset<uint_least32_t> unused_S;
	for (const auto& s : S)	unused_S.insert(s);

	uint_fast32_t x;
	for (x = 0; x != M; ++x)
	{
		const auto itr = unused_S.lower_bound(T[x]);
		if (itr == unused_S.end()) break;
		unused_S.erase(itr);
	}

	return x;
}

[[nodiscard]] static inline uint_fast32_t solve(const uint_fast32_t N, const uint_fast32_t M, const std::vector<uint_least32_t>& S, std::vector<uint_least32_t>& T) noexcept
{
	[[assume(std::is_sorted(S.begin(), S.end()))]];
	const uint_fast32_t x = prepare(N, M, S, T);
	std::sort(T.begin(), T.begin() + x);
	uint_fast32_t ans = 0;
	for (uint_fast32_t i = 0, j = 0; j != x; ++i, ++j)
	{
		while (S[i] < T[j]) ++i;
		ans = std::max<uint_fast32_t>(ans, S[i] - T[j]);
	}

	return ans;
}

int main()
{
	std::cin.tie(nullptr);
	std::ios::sync_with_stdio(false);

	uint_fast32_t N, M;
	std::cin >> N >> M;
	std::vector<uint_least32_t> S(N), T(M);
	for (auto& s : S) std::cin >> s;
	for (auto& t : T) std::cin >> t;

	std::sort(S.begin(), S.end());
	std::cout << solve(N, M, S, T) << '\n';
	return 0;
}