# coding: utf-8
# yuki_198

b=int(raw_input())
n=int(raw_input())
s=[]
for i in xrange(n):
 temp=int(raw_input())
 s.append(temp)
s.sort()
key=min((sum(s)+b)/n,s[n/2])
res=0
for i in xrange(len(s)):
 res+=abs(s[i]-key)
 
print res