#include <bits/stdc++.h>
using namespace std;
int n, m, a[100005], b[100005], r, v;
int main() {
  int i, x;
  scanf("%d %d", &n, &m);
  for (i = 1; i <= n; i++) scanf("%d", &a[i]);
  for (i = 1; i <= m; i++) scanf("%d", &b[i]);
  sort(a + 1, a + n + 1);
  sort(b + 1, b + m + 1);
  for (i = 1; i <= n; i++) {
    v = ((1 << 30) - 1) * 2 + 1;
    x = lower_bound(b + 1, b + m + 1, a[i]) - b;
    if (x <= m && x >= 1) v = min(v, abs(a[i] - b[x]));
    x--;
    if (x <= m && x >= 1) v = min(v, abs(a[i] - b[x]));
    r = max(r, v);
  }
  cout << r;
  return 0;
}
