import sys
input=lambda: sys.stdin.readline().rstrip()
b=int(input())
n=int(input())
C=[int(input()) for _ in range(n)]
l=0
r=(b+sum(C))//n

def ct(x):
  ret=0
  for c in C:
    ret+=abs(c-x)
  return ret


while r-l>2:
  mid1,mid2=l+(r-l)//3,r-(r-l)//3
  if ct(mid1)<ct(mid2):
    r=mid2
  else:
    l=mid1
print(min(ct(l),ct(l+1),ct(r)))