#include <bits/stdc++.h>
using namespace std;
const long long M = 1e9 + 7;
const long long N = 2e5 + 10;
vector<long long> fact(N), ifact(N);
long long inv(long long x) {
  long long res = 1;
  long long b = M - 2;
  while (b) {
    if (b & 1) res = (res * x) % M;
    x = (x * x) % M;
    b >>= 1;
  }
  return res;
}
void init() {
  fact[0] = 1;
  for (long long i = 1; i < N; i++) fact[i] = (fact[i - 1] * i) % M;
  ifact[(long long)2e5] = inv(fact[(long long)2e5]);
  for (long long i = (long long)2e5 - 1; i >= 0; i--)
    ifact[i] = (ifact[i + 1] * (i + 1)) % M;
}
long long ncr(long long n, long long r) {
  if (r > n) return 0;
  long long res = fact[n];
  res = (res * ifact[r]) % M;
  res = (res * ifact[n - r]) % M;
  return res;
}
long long power(long long x, long long y, long long p) {
  long long res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  long long t = 1;
  while (t--) {
    long long n, m;
    cin >> n >> m;
    long long a[100005], b[100005];
    for (int i = 0; i < n; i++) cin >> a[i];
    for (int i = 0; i < m; i++) cin >> b[i];
    int l = 0, max = 0;
    for (int i = 0; i < n; i++) {
      while (abs(b[l] - a[i]) >= abs(b[l + 1] - a[i]) and l < m - 1) {
        l++;
      }
      if (max < abs(b[l] - a[i])) max = abs(b[l] - a[i]);
    }
    cout << max;
  }
  return 0;
}
