N, M = map(int, input().split())
D = [int(input()) for _ in range(M)]

L = [float('inf')]*M
R = [float('inf')]*M

for i in range(M):
    if D[i] < 0:
        L[i] = abs(D[i])
    else:
        R[i] = abs(D[i])
        
L.append(0)
R.append(0)
L.sort()
R.sort()
dp = float('inf')
for i in range(N+1):
    j = N-i
    dp = min(dp, L[i]*2+R[j], L[i]+R[j]*2)
print(dp)