#include <bits/stdc++.h>

[[nodiscard]] static inline constexpr bool check(const uint_fast32_t N, [[maybe_unused]] const uint_fast32_t M, const std::vector<uint_least32_t>& S, const std::vector<std::pair<uint_least32_t, uint_least32_t>>& T, const uint_fast32_t x) noexcept
{
	[[assume(std::is_sorted(S.begin(), S.end()))]];
	[[assume(std::is_sorted(T.begin(), T.end()))]];
	uint_fast32_t i = 0;
	for (const auto& [t, index] : T)
		if (index < x)
		{
			while (i < N && S[i] < t) ++i;
			if (i >= N) return false;
			++i;
		}

	return true;
}

[[nodiscard]] static inline constexpr uint_fast64_t evaluate([[maybe_unused]] const uint_fast32_t N, [[maybe_unused]] const uint_fast32_t M, const std::vector<uint_least32_t>& S, const std::vector<std::pair<uint_least32_t, uint_least32_t>>& T, const uint_fast32_t x) noexcept
{
	[[assume(std::is_sorted(S.begin(), S.end()))]];
	[[assume(std::is_sorted(T.begin(), T.end()))]];
	uint_fast32_t ans = 0, i = 0;
	for (const auto& [t, index] : T)
		if (index < x)
		{
			while (S[i] < t) ++i;
			ans = std::max<uint_fast32_t>(ans, S[i++] - t);
		}

	return ans;
}

[[nodiscard]] static inline constexpr uint_fast64_t solve(const uint_fast32_t N, const uint_fast32_t M, const std::vector<uint_least32_t>& S, const std::vector<std::pair<uint_least32_t, uint_least32_t>>& T) noexcept
{
	[[assume(std::is_sorted(S.begin(), S.end()))]];
	[[assume(std::is_sorted(T.begin(), T.end()))]];
	uint_fast32_t l = 0, r = M + 1;
	while (l + 1 < r)
	{
		const uint_fast32_t x = (l + r) / 2;
		if (check(N, M, S, T, x))
			l = x;
		else
			r = x;
	}

	return evaluate(N, M, S, T, l);
}

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);
	std::vector<std::pair<uint_least32_t, uint_least32_t>> T(M);
	for (auto& s : S) std::cin >> s;
	for (uint_fast32_t i = 0; i < M; ++i) std::cin >> T[i].first, T[i].second = i;

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