#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  VI s(n), t(m);
  rep(i, n) cin >> s[i];
  rep(i, m) cin >> t[i];
  sort(all(s));
  multiset<int> st(all(s));
  VI sc, tc;
  for (int t : t) {
    auto it = st.lower_bound(t);
    if (it == st.end()) break;
    sc.emplace_back(*it);
    tc.emplace_back(t);
    st.erase(it);
  }
  int ans = 0;
  sort(all(sc));
  sort(all(tc));
  rep(i, ssize(sc)) chmax(ans, sc[i] - tc[i]);
  cout << ans << '\n';
}