#include <bits/stdc++.h>
using namespace std;
void SO() { cout << endl; }
template <typename S, typename... Strings>
void SO(S x, const Strings &...rest) {
  cout << x << ' ';
  SO(rest...);
}
const long double PI = 3.1415926535897932384626433832795;
const int v5 = 100000;
const int v9 = 1000000000;
const int v6 = 1000000;
inline long long int ABS(long long int a) {
  if (a < 0) return (-a);
  return a;
}
inline long long int min(long long int a, long long int b, long long int c) {
  return min(a, min(b, c));
}
inline long long int max(long long int a, long long int b, long long int c) {
  return max(a, max(b, c));
}
inline void AI(long long int x[], long long int n) {
  for (long long int i = 0; i < (n); ++i) cin >> (x[i]);
}
inline void VI(vector<long long int> &arr, long long int n) {
  for (long long int i = 0; i < (n); ++i) {
    long long int x;
    cin >> (x);
    arr.push_back(x);
  };
}
long long int n, m, k, c = 0;
long long int a[4000001], b, fk[4000001];
map<long long int, vector<long long int> > g;
long long int BS_UB(long long int (&A)[4000001], long long int target,
                    long long int n) {
  long long int lo = 0, hi = n - 1, best_UB = -1;
  while (lo <= hi) {
    long long int x = (lo + hi) / 2;
    if (A[x] >= target) {
      best_UB = x;
      hi = x - 1;
    } else
      lo = x + 1;
  }
  return best_UB;
}
long long int BS_LB(long long int (&A)[4000001], long long int target,
                    long long int n) {
  long long int lo = 0, hi = n - 1, best_LB = -1;
  while (lo <= hi) {
    long long int x = (lo + hi) / 2;
    if (A[x] <= target) {
      best_LB = x;
      lo = x + 1;
    } else
      hi = x - 1;
  }
  return best_LB;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  cin >> n >> m;
  for (int i = (0); i < (n); ++i) cin >> (fk[i]);
  for (int i = (0); i < (m); ++i) cin >> (a[i]);
  for (int i = (0); i < (n); ++i) {
    long long int b = BS_LB(a, fk[i], m), bb = BS_UB(a, fk[i], m);
    if (b > -1)
      b = ABS(a[b] - fk[i]);
    else
      b = v9 + v9 + 1;
    if (bb > -1) b = min(b, ABS(a[bb] - fk[i]));
    c = max(c, b);
  }
  SO(c);
  return 0;
}
