#include <bits/stdc++.h>

// #include <atcoder/fenwicktree.hpp>
// #include <atcoder/segtree.hpp>
// #include <atcoder/modint.hpp>
// #include <atcoder/dsu.hpp>
// #include <atcoder/lazysegtree.hpp>

// using namespace atcoder;
using namespace std;
using ll = long long;
using ull = unsigned long long;
template <class T>
using max_heap = priority_queue<T>;
template <class T>
using min_heap = priority_queue<T, vector<T>, greater<>>;
ll ll_min = numeric_limits<ll>::min();
ll ll_max = numeric_limits<ll>::max();
ll ALPHABET_N = 26;
// using mint = modint998244353;
#define rep(i, n) for (ll i = (ll)0; i < (ll)n; i++)
#define rep_(i, k, n) for (ll i = (ll)k; i < (ll)n; i++)
#define all(a) a.begin(), a.end()

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	ll n, m;
	cin >> n >> m;
	vector<ll> S(n);
	vector<ll> T(m);
	rep(i, n) cin >> S[i];
	rep(i, m) cin >> T[i];
	ll new_m = 0;
	{
		multiset<ll> st(all(S));
		rep(i, m)
		{
			ll t = T[i];
			auto it = st.lower_bound(t);
			if (it == st.end())
				break;
			new_m++;
			st.erase(it);
		}
	}
	while (T.size() != new_m)
		T.pop_back();
	sort(all(S));
	sort(all(T));
	ll ti = 0;
	ll ans = 0;
	rep(i, n)
	{
		if (ti >= T.size())
			break;
		if (T[ti] <= S[i])
		{
			ans = max(ans, S[i] - T[ti++]);
		}
	}
	cout << ans << endl;
	return 0;
}