import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

import numpy as np

data = np.fromstring(read(), np.int64, sep=' ')

B = data[0]
N = data[1]
C = data[2:]

INF = 10 ** 18

def f(x):
    if C.sum() + B < x * N:
        return INF
    return np.abs(C-x).sum()

cand = C.tolist() + [(B + C.sum())//N]

answer = min(f(x) for x in cand)
print(answer)