#include <bits/stdc++.h>
using namespace std;
int n, m;
int a[110000], b[110000];
int check(long long x) {
  int head = 1;
  for (int i = 1; i <= n; i++) {
    while (abs(b[head] - a[i]) > x && head < m) head++;
    if (abs(b[head] - a[i]) > x) return 0;
  }
  return 1;
}
int main() {
  scanf("%d %d", &n, &m);
  for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
  for (int i = 1; i <= m; i++) scanf("%d", &b[i]);
  sort(a + 1, a + 1 + n);
  sort(b + 1, b + 1 + m);
  long long l = 0, r = 2e9, ans;
  while (l <= r) {
    long long mid = (l + r) / 2;
    if (check(mid))
      ans = mid, r = mid - 1;
    else
      l = mid + 1;
  }
  cout << ans << endl;
  return 0;
}
