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

(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(pair_sums := sorted(a + b for i, a in e(xs) for b in xs[:i])) - 1
    # The pair found by `f` (bisect) could overlap with `a`
    m = min(m, *(abs(goal - (s - a - pair_sums[min(q, bisect(pair_sums, s - a - goal * (n - 3)))]) / (n - 3))
                 for a in xs))
if k >= 4:
    # The pair found by `f` (bisect) could overlap with `a` and/or `b`
    m = min(m, *(abs(goal - (s - a - b - pair_sums[min(q, bisect(pair_sums, s - a - b - goal * (n - 4)))]) / (n - 4))
                 for i, a in e(xs) for b in xs[:i]))
print(m)