B = int(raw_input())
N = int(raw_input())
C = [int(raw_input()) for i in xrange(N)]

ans = 10**18
l, r = -1, 10**18
while r - l > 1:
    m = (l + r) / 2
    b = sum(m - c for c in C)
    if b > B:
        r = m
    else:
        l = m
        ans = min(ans, sum(abs(m - c) for c in C))

for ci in C:
    if sum(ci - c for c in C) > B: continue
    ans = min(ans, sum(abs(ci - c) for c in C))
print ans