import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################
from collections import defaultdict
for _ in range(ni()):
    n, l, k = na()
    x = na()
    ok = (l + 1) // 2
    ng = -1
    X = x + [y + l for y in x]
    while ok - ng > 1:
        mid = ok + ng >> 1
        eve = defaultdict(int)
        for i in range(n):
            L = x[i] - mid
            R = x[i] + mid
            if R >= l:
                eve[L] += 1
                eve[0] += 1
                eve[R-l] -= 1
            elif L < 0:
                eve[L + l] += 1
                eve[0] += 1
                eve[R] -= 1
            else:
                eve[L] += 1
                eve[R] -= 1
            
        flag = 1
        s = 0
        for y in sorted(eve):
            s += eve[y]
            if s < k:
                flag = 0
                break
        # print(mid, flag, [(y, eve[y]) for y in sorted(eve)])
        if flag:
            ok = mid
        else:
            ng = mid
    
    print(ok)