T=int(input())
for _ in range(T):
  n,L,K=map(int,input().split())
  xs=list(map(int,input().split()))
  if L==1:
    print(1)
    continue
  ok=(L//2)+1
  ng=0
  while ok-ng>1:
    m=(ok+ng)//2
    p=[]
    z=[0,L]
    for x in xs:
      l=x-m
      r=x+m-1
      if 0<=l<=r<L:
        p+=[(l,r+1)]
        z+=[l,r+1]
      elif 0<=l<L<=r:
        p+=[(l,L-1+1),(0,(r-L+1)-1+1)]
        z+=[l,L-1+1,0,(r-L+1)-1+1]
      else:
        p+=[(L-1-(0-l)+1,L-1+1),(0,r+1)]
        z+=[L-1-(0-l)+1,L-1+1,0,r+1]
    z=sorted(set(z))
    d={v:i for i,v in enumerate(z)}
    q=[0]*len(z)
    for l,r in p:
      q[d[l]]+=1
      q[d[r]]-=1
    for i in range(1,len(q)):
      q[i]+=q[i-1]
    if min(q[:d[L]])>=K:
      ok=m
    else:
      ng=m
  print(ok)