n,m=gets.chomp.split.map(&:to_i)
ds = m.times.map{ gets.to_i }

xs = ds.select{|x| x < 0 }.map{|x| -x}.sort
ys = ds.select{|x| x > 0 }.sort

if ds.select{|x| x == 0}.length > 0
  n -= 1
end

ans = 1e10

if xs.size >= n
  ans = [ans, xs[n-1]].min
end
if ys.size >= n
  ans = [ans, ys[n-1]].min
end

for k in 0..xs.size do
  if k < n
    d = (k == 0 ? 0 : xs[k-1]) * 2 + (n==k ? 0 : ys[n-k-1])
    ans = [ans, d].min
  end
end

xs,ys = ys,xs

for k in 0..xs.size do
  if k < n
    d = (k == 0 ? 0 : xs[k-1]) * 2 + (n==k ? 0 : ys[n-k-1])
    ans = [ans, d].min
  end
end

p ans