import heapq 
from heapq import heappop,heappush,heapify
from sys import stdin, setrecursionlimit
input = stdin.readline
readline = stdin.readline
from collections import deque,defaultdict

from collections import deque
d=deque()


T=int(input())
for i in range(T):
  N,L,K=map(int, input().split())
  A=list(map(int, input().split()))
  A=sorted(A)
  ng,ok=0,L+1
  while ok-ng>1:
    mid=(ok+ng)//2
    C=[0,L]
    D={}
    D[0]=0
    D[L]=0
    for a in A:
      if a-mid>=0:
        if a-mid not in D:
          D[a-mid]=0
        D[a-mid]+=1
        C.append(a-mid)
      else:
        D[0]+=1
        if a-mid+L not in D:
          D[a-mid+L]=0
        D[a-mid+L]+=1
        C.append(a-mid+L)
      if a+mid<L:
        r=a+mid
        if r not in D:
          D[r]=0
        D[r]-=1
        C.append(r)
      else:
        D[0]+=1
        if a+mid-L not in D:
          D[a+mid-L]=0
        D[a+mid-L]-=1
        C.append(a+mid-L)
      C=sorted(list(set(C)))
    c=0;f=1
    for i in range(len(C)-1):
      c+=D[C[i]]
      if c<K:
        f=0
        break
    if f:
      ok=mid 
    else:
      ng=mid
  print(ok)