#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 20;
long long int n, m, a[N], b[N], maxi, r;
int main() {
  cin >> n >> m;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  sort(a, a + n);
  for (int i = 0; i < m; i++) {
    cin >> b[i];
  }
  sort(b, b + m);
  if (m == 1) {
    for (int i = 0; i < n; i++) {
      maxi = max(maxi, abs(b[0] - a[i]));
    }
    cout << maxi;
    return 0;
  }
  for (int i = 0; i < n; i++) {
    if (abs(b[r] - a[i]) < abs(b[r + 1] - a[i])) {
      maxi = max(maxi, abs(b[r] - a[i]));
    } else {
      while (abs(b[r] - a[i]) >= abs(b[r + 1] - a[i]) && r + 1 < m - 1) {
        r++;
      }
      if (abs(b[r] - a[i]) < abs(b[r + 1] - a[i])) {
        maxi = max(maxi, abs(b[r] - a[i]));
      } else {
        maxi = max(maxi, abs(b[r + 1] - a[i]));
      }
    }
  }
  cout << maxi;
  return 0;
}
