b=int(input())
n=int(input())
C=[int(input()) for _ in range(n)]

def cnt(x):
    return sum(abs(c-x) for c in C)

ng,ok=-1,(sum(C)+b)//n
while ok-ng>2:
    mid1=(ng*2+ok)//3
    mid2=(ng+ok*2)//3
    
    if cnt(mid1)<cnt(mid2):
        ok=mid2
    else:
        ng=mid1

print(cnt(ok) if n!=1 else 0)