#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
bool ss(int k, const vector<int>& trees, const vector<int>& sprinklers) {
    int m = sprinklers.size();
    int n = trees.size();
    int i = 0, j = 0;
        while (i < n) {
        if (j < m && trees[i] >= sprinklers[j] - k && trees[i] <= sprinklers[j] + k) {
            i++; 
        } else if (j < m && trees[i] > sprinklers[j] + k) {
            j++; 
        } else {
            return false;  
        }
    }
    
    return true;  
}

int main() {
    int N, M;
    cin >> N;
    vector<int> trees(N);
    for (int i = 0; i < N; i++) {
        cin >> trees[i];
    }
    cin >> M;
    vector<int> sprinklers(M);
    for (int i = 0; i < M; i++) {
        cin >> sprinklers[i];
    }
    sort(trees.begin(), trees.end());
    sort(sprinklers.begin(), sprinklers.end());
        int left = 0;
    int right = max(abs(trees.back() - sprinklers.front()), abs(sprinklers.back() - trees.front()));
    int result = right;
    
    while (left <= right) {
        int mid = (left + right) / 2;
                if (ss(mid, trees, sprinklers)) {
            result = mid; 
            right = mid - 1;
        } else {
            left = mid + 1; 
        }
    }
        cout << result << endl;
    
    return 0;
}

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int solve(vector<int>& arr, int k) {
    sort(arr.begin(), arr.end());
    int i = 0, j = arr.size() - 1;
    int moves = 0;
    while (i <= j) {
        if (arr[i] + arr[j] <= k) {
            i++;
            j--;
        } else {
            j--;
        }
        moves++; 
    }
    
    return moves;
}