func main()
	var n: int :: cui@inputInt()
	var m: int :: cui@inputInt()
	var a: []int :: #[m + 1]int
	for i(0, m - 1)
		do a[i] :: cui@inputInt()
	end for
	do a[m] :: 0
	do a.sort()
	var ans: int :: lib@intMax
	for i(0, m - n)
		var l: int :: a[i] * -1
		var r: int :: a[i + n]
		if(l * r >= 0)
			do ans :: [ans, [l * 2 + r, l + r * 2].min()].min()
		end if
	end for
	do cui@print("\{ans}\n")
end func