#!/usr/bin/env python3
from bisect import bisect


def find(target, used):
    i = min(q, bisect(ps, (target, 0)))
    return (p[0] for p in ps[max(0, i - 1):i + 1] if all(j not in used for j in p[1:]))


(n, k, goal), xs = (list(map(int, input().split())) for _ in "__")
m, e = abs(goal - (s := sum(xs)) / n), enumerate
if k >= 1: m = min(m, *(abs(goal - (s - a) / (n - 1)) for a in xs))
if k >= 2: m = min(m, *(abs(goal - (s - a - b) / (n - 2)) for i, a in e(xs) for b in xs[:i]))
if k >= 3:
    q = len(ps := sorted(((a + b, i, j) for i, a in e(xs) for j, b in e(xs[:i])), key=lambda t: t[0])) - 1
    # Passing `m` twice, in case the generator is empty, because `min(m, *[])` throws an error in Python
    m = min(m, m, *(abs(goal - (s - a - p) / (n - 3)) for i, a in e(xs) for p in find(s - a - goal * (n - 3), (i,))))
if k >= 4: m = min(m, m, *(abs(goal - (s - a - b - p) / (n - 4))
                           for i, a in e(xs) for j, b in e(xs[:i]) for p in find(s - a - b - goal * (n - 4), (i, j))))
print(m)