void Main()
{
	var tasks = new[]
	{
		Task.FromResult(new [] {1, 2, 3}.Select(x => Task.FromResult(x))),
		Task.FromResult(new [] {4, 5, 6}.Select(x => Task.FromResult(x))),
	};

	tasks.SelectManyAsync().Select(t => t.GetAwaiter().GetResult()).Dump();
}