#!/usr/bin/env python3
(n, k, goal), xs = (list(map(int, input().split())) for _ in "__")
for _ in range(k):
    avg = sum(xs) / len(xs)
    i = min(range(len(xs)), key=lambda i: abs(goal - (avg * len(xs) - xs[i]) / (len(xs) - 1)))
    xs = xs[:i] + xs[i + 1:]
print(abs(goal - sum(xs) / len(xs)))