n, m = map(int, input().split())
D = [int(input()) for i in range(m)]
N = []
P = []
for d in D:
    if d < 0:
        N.append(abs(d))
    else:
        P.append(d)
P.sort()
N.sort()

ans = 10**18
for i in range(0, len(P)+1):
    if i > n:
        continue
    j = n-i
    if j > len(N):
        continue
    if i == 0:
        temp = N[j-1]
    elif j == 0:
        temp = P[i-1]
    else:
        temp = min(2*P[i-1]+N[j-1], P[i-1]+2*N[j-1])
    ans = min(ans, temp)
print(ans)