INF = 10 ** 9
n,m = gets.split.map(&:to_i)
d = m.times.map { gets.to_i }
d.push(0)
a = d.select {|v| v >= 0 }.sort
b = d.select {|v| v <= 0 }.map {|v| v.abs }.sort

dp = Array.new(n+1,INF)

(0..n).each do |i|
    j = n - i
    if i < a.size && j < b.size
        dp[i] = a[i] < b[j] ? a[i] * 2 + b[j] : a[i] + b[j] * 2
    end
end

puts dp.min