#include <bits/stdc++.h>
using namespace std;
bool debug = 0;
int n, m, k;
int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};
string direc = "RDLU";
long long ln, lk, lm;
void etp(bool f = 0) {
  puts(f ? "YES" : "NO");
  exit(0);
}
void addmod(int &x, int y, int mod = 1000000007) {
  x += y;
  if (x >= mod) x -= mod;
}
void et() {
  puts("-1");
  exit(0);
}
long long a[100005], b[100005];
bool ck(long long r) {
  for (int(i) = 1; (i) <= (int)(n); (i)++) {
    long long L = a[i] - r, R = a[i] + r;
    int p = upper_bound(b + 1, b + 1 + m, R) - (b + 1);
    p--;
    int q = lower_bound(b + 1, b + 1 + m, L) - (b + 1);
    q--;
    if (q >= p) return 0;
  }
  return 1;
}
void fmain() {
  scanf("%d%d", &n, &m);
  for (int(i) = 1; (i) <= (int)(n); (i)++) {
    scanf("%lld", a + i);
  }
  for (int(i) = 1; (i) <= (int)(m); (i)++) scanf("%lld", b + i);
  long long l = -1, r = 2e9;
  while (l + 1 < r) {
    long long mid = (l + r) / 2;
    if (ck(mid))
      r = mid;
    else
      l = mid;
  }
  printf("%lld\n", r);
}
int main() {
  fmain();
  return 0;
}
