#include <bits/stdc++.h>
using namespace std;
const long long N = 1e5 + 10;
long long a[N], b[N];
void minimize(long long &u, long long v) { u = min(u, v); }
int main() {
  long long n, m;
  scanf("%I64d %I64d", &n, &m);
  for (long long i = 1; i <= n; i++) scanf("%I64d", &a[i]);
  for (long long i = 1; i <= m; i++) scanf("%I64d", &b[i]);
  sort(b + 1, b + m + 1);
  long long ans = 0;
  for (long long i = 1; i <= n; i++) {
    long long pos = lower_bound(b + 1, b + 1 + m, a[i]) - b;
    long long cur = 2e9;
    for (long long j = max(1LL, pos - 1); j <= min(m, pos + 1); j++) {
      minimize(cur, abs(b[j] - a[i]));
    }
    ans = max(ans, cur);
  }
  cout << ans << endl;
}
