import sys

sys.setrecursionlimit(200005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

# dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = -1-(-1 << 31)
inf = -1-(-1 << 62)

# md = 10**9+7
md = 998244353

from collections import defaultdict

def solve():
    def binary_search(l, r, minimize):
        if minimize: l -= 1
        else: r += 1
        while l+1 < r:
            m = (l+r)//2
            if ok(m) ^ minimize: l = m
            else: r = m
        if minimize: return r
        return l

    def ok(m):
        # print(m)
        cs = defaultdict(int)
        for x in xx:
            l = x-m
            r = min(x+m, l+L)
            if l<0:
                cs[l+L]+=1
                l=0
            cs[l]+=1
            if r>L:
                cs[0]+=1
                r-=L
            cs[r] -= 1
        s=0
        for i in sorted(cs):
            s+=cs[i]
            if s<k:return False
        return True

    n, L, k = LI()
    xx = LI()
    ans = binary_search(1, (L+1)//2, True)
    print(ans)

for _ in range(II()): solve()