#include <bits/stdc++.h>
const int Inf = 2 * 1000 * 1000 * 1000;
long long LINF = (long long)4e18;
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int n, m;
  cin >> n >> m;
  vector<int> a(n);
  vector<int> b(m);
  for (auto &x : a) cin >> x;
  for (auto &x : b) cin >> x;
  sort((a).begin(), (a).end());
  sort((b).begin(), (b).end());
  long long l = 0, r = 2e9;
  while (l < r) {
    long long m = (l + r) / 2;
    int ok = 1;
    for (auto &x : a) {
      auto left = lower_bound((b).begin(), (b).end(), x - m);
      auto right = lower_bound((b).begin(), (b).end(), x);
      if (left != b.end()) {
        long long dist = abs(*left - x);
        if (dist <= m) continue;
      }
      if (right != b.end()) {
        long long dist = abs(*right - x);
        if (dist <= m) continue;
      }
      ok = 0;
      break;
    }
    if (ok)
      r = m;
    else
      l = m + 1;
  }
  cout << l;
  return 0;
}
