#include <bits/stdc++.h>
using namespace std;
const int MAX = 1e5 + 10;
long long arr[MAX], arr2[MAX];
int n, m;
bool check(long long mid) {
  int prv = 0;
  for (int i = 0; i < n; ++i) {
    while (prv < m && arr2[prv] + mid < arr[i]) ++prv;
    if (prv == m || arr2[prv] - mid > arr[i]) return 0;
  }
  return 1;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cin >> n >> m;
  for (int i = 0; i < n; ++i) cin >> arr[i];
  for (int i = 0; i < m; ++i) cin >> arr2[i];
  sort(arr, arr + n);
  sort(arr2, arr2 + m);
  long long l = 0, r = 2e9;
  long long ans = r;
  while (l <= r) {
    long long mid = (l + r) >> 1;
    if (check(mid))
      ans = mid, r = mid - 1;
    else
      l = mid + 1;
  }
  return cout << ans << "\n", 0;
}
