#include <iostream>
#include <vector>
#include <set>
#include <algorithm>

void chmax(int &a, int b) {
    if (a < b) a = b;
}

int main() {
    int N, M;
    std::cin >> N >> M;
    std::vector<int> S(N), T(M);
    for (int &s : S) std::cin >> s;
    for (int &t : T) std::cin >> t;
    std::multiset<int> set(S.begin(), S.end());

    int best = 0;
    for (int t : T) {
        auto iter = set.lower_bound(t);
        if (iter == set.end()) break;
        set.erase(iter);
        best++;
    }

    T.resize(best);
    std::sort(T.begin(), T.end());
    set = std::multiset<int>(S.begin(), S.end());

    int result = 0;
    for (int t : T) {
        auto iter = set.lower_bound(t);
        if (iter == set.end()) break;
        chmax(result, *iter - t);
        set.erase(iter);
    }

    std::cout << result << std::endl;
}