#include <bits/stdc++.h>
using namespace std;
long long inv(long long a, long long p) {
  long long temp = 1;
  while (p != 0) {
    if (p % 2 == 1) temp = (temp * a) % (long long)(1e9 + 7);
    a = ((long long)a * a) % (long long)(1e9 + 7);
    p = p / 2;
  }
  return temp;
}
int main() {
  ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  long long a[100009], b[100009];
  long long n, m;
  cin >> n >> m;
  for (int i = 0; i < n; i++) cin >> a[i];
  for (int i = 0; i < m; i++) cin >> b[i];
  long long l = 0, r = 10000000000;
  long long mid = (l + r) / 2;
  while (l < r) {
    long long ind1 = 0, ind2 = 0;
    long long f = 0;
    for (ind1 = 0; ind1 < n; ind1++) {
      while ((ind2 < m - 1) &&
             (b[ind2 + 1] - a[ind1]) * (b[ind2 + 1] - a[ind1]) <=
                 (b[ind2] - a[ind1]) * (b[ind2] - a[ind1]))
        ind2++;
      if ((b[ind2] - a[ind1]) * (b[ind2] - a[ind1]) > mid * mid) f = 1;
    }
    if (f == 1)
      l = mid + 1;
    else
      r = mid;
    mid = (l + r) / 2;
  }
  cout << mid;
  return 0;
}
