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

using namespace std;

int main()
{
  int t;
  cin >> t;
  while (t--)
  {
    int n, l, k;
    cin >> n >> l >> k;
    vector<int> a(2 * n);
    for (int i = 0; i < n; ++i) cin >> a[i];
    for (int i = 0; i < n; ++i) a[i + n] = a[i] + l;
    sort(a.begin(), a.end());
    int ma = 0;
    for (int i = 0; i < n; ++i) ma = max(a[i + k] - a[i], ma);
    ma = (ma + 1) / 2;
    cout << ma << endl;
  }
}