# pragma GCC target("avx2")
# pragma GCC optimize("O3")
# pragma GCC optimize("unroll-loops")

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

using namespace std;

int a[40000];

int main()
{
  int t;
  scanf("%d", &t);
  while (t--)
  {
    int n, l, k;
    scanf("%d%d%d", &n, &l, &k);
    for (int i = 0; i < n; ++i) scanf("%d", &a[i]);
    for (int i = 0; i < n; ++i) a[i + n] = a[i] + l;
    sort(a, a + 2 * n);
    int ma = 0;
    for (int i = 0; i < n; ++i) ma = max(a[i + k] - a[i], ma);
    ++ma;
    ma >>= 1;
    printf("%d\n", ma);
  }
}