static void Main(string[] args)
{
Q18 q = new Q18();
Console.WriteLine(q.FourSum(new int[] { 1, 0, -1, 0, -2, 2 }, 0));
int a = 1, b = 2;
a = b + (b = a) * 0;
Console.WriteLine($"a:{a} b:{b}");
}
