//TLE解
//O(NlogN+MlogM+M^2logN)
#include <iostream>
#include <algorithm>
#include <atcoder/all>
#include <set>
using namespace std;
using namespace atcoder;
using ll = long long;
//#define endl "\n";
ll N, M, A[200009], B[200009];

int main(){
  cin >> N >> M;
  for(int i = 0; i < N; i++) cin >> A[i];
  for(int i = 0; i < M; i++) cin >> B[i];
  sort(A, A + N);
  multiset<ll> mst;
  ll ans = 0;
  for(int i = 0; i < M; i++){
    mst.insert(B[i]);
    ll pos = 0, ret = 0;
    bool isOK = true;
    for(auto itr = mst.begin(); itr != mst.end(); ++itr){
      pos = lower_bound(A + pos, A + N, *itr) - A;
      if(pos >= N){
        isOK = false;
        break;
      }
      ret = max(ret, abs(*itr - A[pos]));
      pos++;
    }
    if(isOK) ans = ret;
    else break;
  }
  cout << ans << endl;
  return 0;
}