def f(CB, m):
    s = 0
    for c in CB:
        s += abs(m - c)
    return s

B = int(input())
N = int(input())
if N == 1:
    print(0)
else:
    CB = [int(input()) for _ in range(N)]
    l = min(CB)
    r = (sum(CB)+B) / N
    while r - l >= 1:
        lm = (2*l + r) / 3
        rm = (l + 2*r) / 3
        if f(CB, lm) > f(CB, rm):
            l = lm
        else:
            r = rm
    print(f(CB, int(r)))