#!/usr/bin/python2
# -*- coding: utf-8 -*-
# †
# (ΦωΦ)＜左からi個、右からN-i個取ることにする。
#
n, m = map(int, raw_input().split())
a = [int(raw_input()) for _ in xrange(m)]
lh = sorted([abs(x) for x in a if x < 0])
rh = sorted([x for x in a if x >= 0])
M = len(lh)
N = len(rh)

mini = float('inf')
if 0 <= n-1 < N: # i==0
    mini = min(mini, rh[n-1])
if 0 <= n-1 < M: # i==n
    mini = min(mini, lh[n-1])

for i in xrange(1, n):
    if 0 <= i-1 < M and 0 <= n-i-1 < N:
        mini = min(mini, lh[i-1] * 2 + rh[n-i-1], lh[i-1] + rh[n-i-1] * 2)
print mini