N,M = map(int,input().split())
D = [int(input()) for _ in range(M)]
D.sort()
ans = (1<<60)
M,N = N,M
for i in range(N-M+1):
    
    tmp1 = abs(D[i]) + D[i+M-1] - D[i]
    tmp2 = abs(D[i+M-1]) + D[i+M-1] - D[i]
    ans = min(ans,tmp1,tmp2)
    
print(ans)