#include <bits/stdc++.h>
using namespace std;
const int N = int(1e5 + 100);
long long a[N], b[N], n, m;
bool oki_doki(long long x) {
  long long pos = 0;
  for (int i = 0; i < n; i++) {
    long long l = a[i] - x, r = a[i] + x;
    while (pos < m && b[pos] < l) pos++;
    if (pos == m || b[pos] > r) return 0;
  }
  return 1;
}
int main() {
  long long l = 0, r = 2e9 + 1;
  cin >> n >> m;
  for (int i = 0; i < n; i++) cin >> a[i];
  for (int i = 0; i < m; i++) cin >> b[i];
  sort(a, a + n);
  sort(b, b + m);
  while (l != r) {
    long long mid = (l + r) / 2;
    if (oki_doki(mid))
      r = mid;
    else
      l = mid + 1;
  }
  cout << l;
  return 0;
}
