#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 5;
const long long INF = 0x3f3f3f3f3f3f3f3f;
const double eps = 1e-8;
int n, m, a[MAXN], b[MAXN];
int rel(int i, int j, long long r) {
  long long L = b[j] - r, R = b[j] + r;
  if (a[i] < L) return -1;
  if (a[i] > R) return 1;
  return 0;
}
bool ok(long long r) {
  if (rel(1, 1, r) == -1) return false;
  for (int i = 1, j = 1; i <= n; i++) {
    while (j <= m && rel(i, j, r) == 1) j++;
    if (j > m || rel(i, j, r) == -1) return false;
  }
  return true;
}
inline void run() {
  cin >> n >> m;
  for (int i = 1; i <= n; i++) cin >> a[i];
  for (int i = 1; i <= m; i++) cin >> b[i];
  sort(a + 1, a + n + 1), sort(b + 1, b + m + 1);
  n = unique(a + 1, a + n + 1) - a - 1;
  m = unique(b + 1, b + m + 1) - b - 1;
  long long l = 0, r = 2e9, mid, res = 0;
  while (l <= r) {
    mid = l + r >> 1;
    if (ok(mid))
      r = (res = mid) - 1;
    else
      l = mid + 1;
  }
  cout << (res) << '\n';
}
int main() {
  run();
  return 0;
}
