#include <bits/stdc++.h>
using namespace std;
long long int arr[100010];
long long int cel[100010];
int n, m;
bool cal(long long int val) {
  int st = 0;
  int cnt = 0;
  for (int i = 0; i < m; i++) {
    if (cnt == n) return 1;
    long long int m = cel[i];
    long long int p = m + val;
    long long int q = m - val;
    for (int j = st; j < n; j++) {
      if (arr[j] >= q && arr[j] <= p) {
        cnt++;
      } else {
        st = j;
        break;
      }
    }
  }
  if (cnt == n) return 1;
  return 0;
}
int main() {
  scanf("%d %d", &n, &m);
  for (int i = 0; i < n; i++) {
    scanf("%lld", &arr[i]);
  }
  for (int i = 0; i < m; i++) {
    scanf("%lld", &cel[i]);
  }
  long long int low = 0;
  long long int high = 2000000000;
  long long int mid;
  while (low <= high) {
    mid = (low + high) >> 1;
    if (cal(mid)) {
      high = mid - 1;
    } else
      low = mid + 1;
  }
  printf("%lld\n", low);
}
