B = int(input())
N = int(input())
l = []

for i in range(N):
    l.append(int(input()))
cnady_n = sum(l) + B
box_max_candy = cnady_n // N

n_median = 0
n_median1 = 0
s = set(l)
if len(s) % 2 == 0:
    n_median = len(s) // 2 
    n_median1 = n_median - 1
else:
    n_median = (len(s) -1) // 2
ll = list(s)
ll.sort()
#print(n_median,n_median1)
ck = ll[n_median]
ck1 = ll[n_median1]
#print(ck,ck1)
ans = 0
ans1 = 0
ans2 = 0
for l_i in l:
    ans += abs(l_i - ck)
    ans1 += abs(l_i - ck1)
    ans2 += abs(l_i - box_max_candy)

if ck > box_max_candy:
    ans = 1000000000000000
if ck1 > box_max_candy:
    ans1 = 10000000000000
print(min(ans,ans1,ans2))
#print(box_max_candy)