B=int(input())
N=int(input())
C=[]
for i in range(N):
    C.append(int(input()))

C.sort()
S=sum(C)
T=0

Z=0
K=(S//N)*N
if  (S//N != (S+B)//N) and S-K>=K+N-S:
    U=K+N-S

    i=0
    while U>0:
        D=min(U,C[i]-S//N+1)
        Z+=D
        C[i]+=D
        U-=D
        i+=1

S=sum(C)
for i in range(N):
    Z+=abs(C[i]-S//N)

print(Z)