#include <bits/stdc++.h>
using namespace std;
template <class T>
ostream& operator<<(ostream& os, vector<T> V) {
  os << "[ ";
  for (auto v : V) os << v << " ";
  return os << "]";
}
template <class T>
ostream& operator<<(ostream& os, set<T> S) {
  os << "{ ";
  for (auto s : S) os << s << " ";
  return os << "}";
}
template <class L, class R>
ostream& operator<<(ostream& os, pair<L, R> P) {
  return os << "(" << P.first << "," << P.second << ")";
}
template <class L, class R>
ostream& operator<<(ostream& os, map<L, R> M) {
  os << "{ ";
  for (auto m : M) os << "(" << m.first << ":" << m.second << ")";
  return os << "}";
}
template <typename Arg1>
void __f(const char* name, Arg1&& arg1) {
  cout << name << " : " << arg1 << std::endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args) {
  const char* comma = strchr(names + 1, ',');
  cout.write(names, comma - names) << " : " << arg1 << " | ";
  __f(comma + 1, args...);
}
const int mod = 1e9 + 7;
inline int add(int a, int b) {
  a += b;
  if (a >= mod) a -= mod;
  return a;
}
inline int sub(int a, int b) {
  a -= b;
  if (a < 0) a += mod;
  return a;
}
inline int mul(int a, int b) { return a * 1ll * b % mod; }
inline int power(int x, long long y) {
  int res = 1;
  while (y) {
    if (y & 1) res = mul(res, x);
    x = mul(x, x);
    y >>= 1;
  }
  return res;
}
const int N = 1e5 + 100;
long long A[N], B[N];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  cout << fixed << setprecision(25);
  int n, m;
  cin >> n >> m;
  for (int i = 1; i <= n; ++i) cin >> A[i];
  for (int i = 1; i <= m; ++i) cin >> B[i];
  long long lo = 0, hi = 2000000000, ans = hi;
  while (lo <= hi) {
    long long r = (lo + hi) >> 1;
    int j = 1;
    for (int i = 1; i <= m; ++i) {
      while (j <= n && abs(A[j] - B[i]) <= r) ++j;
    }
    if (j == n + 1) {
      ans = r;
      hi = r - 1;
    } else
      lo = r + 1;
  }
  cout << ans << "\n";
  return 0;
}
