import std.algorithm, std.conv, std.range, std.stdio, std.string;

void main()
{
  auto rd1 = readln.split.to!(int[]), n = rd1[0], m = rd1[1];
  auto d = new int[](m);
  foreach (i; 0..m) d[i] = readln.chomp.to!int;

  auto d1 = d.filter!"a > 0".array.sort().array;
  auto d2 = d.filter!"a < 0".map!"-a".array.sort().array;

  if (d.canFind(0)) --n;

  if (n == 0) {
    writeln(0);
    return;
  }

  writeln(min(calc(n, d1, d2), calc(n, d2, d1)));
}

auto calc(int n, int[] a, int[] b)
{
  if (a.length == 0) return int.max;

  auto r = a[n-1];

  foreach (i; 1..min(a.length, n))
    if (n-i < b.length)
      r = min(r, a[i-1] * 2 + b[n-i-1]);

  return r;
}