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[i] for i in xrange(N))
    if b > B:
        r = m
    else:
        l = m
        ans = min(ans, sum(abs(C[i] - m) for i in xrange(N)))
print ans