// やけくそTLE解.

//#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define all(a) (a).begin(), (a).end()
const ll INF32 = 2e9;
const ll INF64 = 4e18;

void printYN(bool ok){
    if(ok)cout << "Yes" << endl;
    else cout << "No" << endl;
    return;
}

signed main() {
    int N, M;
    cin >> N >> M;
    vector<int> S(N), T(M);
    rep(i, N)cin >> S[i];
    rep(i, M)cin >> T[i];
    multiset<int> SS;
    vector<int> Staizi, Ttaizi;
    rep(i, N){
        SS.insert(S[i]);
    }
    rep(i, M){
        auto it = SS.lower_bound(T[i]);
        if(it==SS.end())break;
        Staizi.push_back(*it);
        Ttaizi.push_back(T[i]);
        SS.erase(it);
    }
    sort(all(Staizi));
    sort(all(Ttaizi));
    int ans = 0;
    rep(i, Staizi.size()){
        ans = max(ans, Staizi[i]-Ttaizi[i]);
    }
    cout << ans << endl;
    return 0;
}