#include <bits/stdc++.h>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N, M;
    cin >> N >> M;

    vector<long long> S(N), T(M);
    for (int i = 0; i < N; i++) cin >> S[i];
    for (int i = 0; i < M; i++) cin >> T[i];

    if (T[0] > *max_element(S.begin(), S.end())) {
        cout << 0 << "\n";
        return 0;
    }

    multiset<long long> L(S.begin(), S.end());
    vector<long long> TT;

    for (auto i : T) {
        auto it = L.lower_bound(i);
        if (it == L.end()) break;
        L.erase(it);
        TT.push_back(i);
    }

    sort(TT.begin(), TT.end());
    L = multiset<long long>(S.begin(), S.end());

    long long ans = 0;
    for (auto i : TT) {
        auto it = L.lower_bound(i);
        long long a = *it;
        L.erase(it);
        ans = max(ans, a - i);
    }

    cout << ans << "\n";
    return 0;
}