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
  
  while ok-ng>1:
    mid=(ok+ng)//2
    C=[0,L]
    D=defaultdict(int)
    for a in A:
      if a-mid>=0:
        D[a-mid]+=1
        C.append(a-mid)
      else:
        D[0]+=1
        D[a-mid+L]+=1
        C.append(a-mid+L)
      if a+mid<L:
        r=a+mid
        D[r]-=1
        C.append(r)
      else:
        D[0]+=1
        D[a+mid-L]-=1
        C.append(a+mid-L)
      C=sorted(list(set(C)))
    c=0
    he=10**10
    for i in range(len(C)-1):
      c+=D[C[i]]
      he=min(he,c)
    if he>=K:
      ok=mid 
    else:
      ng=mid
  print(ok)