#include <bits/stdc++.h>
using namespace std;
const int maxn = 100010;
int n, m;
long long a[maxn], b[maxn];
bool cal(long long r) {
  int j, i;
  for (i = 0, j = 0; j < m; j++) {
    while (i < n && abs(a[i] - b[j]) <= r) i++;
  }
  return i >= n ? true : false;
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 0; i < n; i++) {
    scanf("%lld", &a[i]);
  }
  for (int i = 0; i < m; i++) {
    scanf("%lld", &b[i]);
  }
  long long l = 0, r = 2000000000;
  long long ans = 0;
  while (l <= r) {
    int mid = (l + r) / 2;
    if (cal(mid)) {
      ans = mid;
      r = mid - 1;
    } else
      l = mid + 1;
  }
  printf("%lld\n", ans);
  return 0;
}
