#include <bits/stdc++.h>
using namespace std;
const int M = 1e5 + 5;
int a[M], b[M];
int n, m;
int fr(int x) {
  int l = 1, r = m, mid;
  while (l <= r) {
    mid = l + r >> 1;
    if (b[mid] > x)
      r = mid - 1;
    else
      l = mid + 1;
  }
  if (r == 0) r = 1;
  return r;
}
int fl(int x) {
  int l = 1, r = m, mid;
  while (l <= r) {
    mid = l + r >> 1;
    if (b[mid] < x)
      l = mid + 1;
    else
      r = mid - 1;
  }
  if (l > m) l = m;
  return l;
}
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]);
  int ans = 0;
  int l, r;
  for (int i = 1; i <= n; ++i) {
    l = fl(a[i]);
    r = fr(a[i]);
    ans = max(ans, min(abs(b[l] - a[i]), abs(b[r] - a[i])));
  }
  printf("%d\n", ans);
  return 0;
}
