#include <bits/stdc++.h>
using namespace std;

int main() {
  int N, M, Ans = 0; cin >> N >> M;
  vector<int> A, B;
  map<int, int> Acsta;
  for (int i = 0; i < N; i++) {
    int S; cin >> S;
    Acsta[S]++;
  }
  for (int i = 0; i < M; i++) {
    int T; cin >> T;
    auto it = Acsta.lower_bound(T);
    if (it == Acsta.end()) break;
    A.push_back(it->first);
    B.push_back(T);
    it->second--;
    if (it->second == 0)
      Acsta.erase(it);
  }
  sort(A.begin(), A.end());
  sort(B.begin(), B.end());
  for (int i = 0; i < (int)A.size(); i++)
    Ans = max(Ans, A.at(i) - B.at(i));
  cout << Ans << endl;
}