B = int(input())
N = int(input())
C = [int(input()) for _ in range(N)]
low = 0
high = (sum(C)+B)//N
while high-low>1e-5:
    l = (2*low+high)/3
    r = (low+2*high)/3
    ml = 0
    mr = 0
    for i in range(N):
        ml += abs(C[i]-l)
        mr += abs(C[i]-r)
    if mr>=ml:
        high = r
    else:
        low = l
ml = 0
mr = 0
high = int(high)
if high>=1:
    low = high-1
else:
    low = 0
for i in range(N):
    ml += abs(C[i]-low)
    mr += abs(C[i]-high)
print(min(ml,mr))