N,m=map(int,input().split())
M=[]
P=[]
Z=0
for i in range(m):
    x=int(input())

    if x==0:
        Z+=1
    elif x<0:
        M.append(-x)
    else:
        P.append(x)

M.append(0)
P.append(0)

M.sort()
P.sort()

N-=Z

if N<=0:
    print(0)
    exit()

ANS=1<<63

for i in range(len(M)):
    j=N-i
    if j<len(P):
        ANS=min(ANS,M[i]*2+P[j],M[i]+P[j]*2)

print(ANS)