b,n,*a = map(int,open(0).read().split())
m = (sum(a)+b)//n
ans = 1<<60
for x in a+[0,m]:
    more = less = 0
    for ai in a:
        if ai >= x: more += ai - x
        else: less += x - ai
    if more + b < less: continue
    ans = min(ans, more+less)
print(ans)