In J, how can I find the extended precision integer floor square root

I understand that when I take the square root ( %:

) of a number that does not result in an integer, my answer is a float. I'm looking to find the floor ( <.

) of a square root to get an integer result. Does J have a built-in way to achieve this? Do I need to loop over to find the answer?

Dropping in multiple queries with extended precision ( x:

) certainly doesn't do this.

   rootanddiffa =: 3 : '(y - root ^ 2);(root =. <. %: y)'
   rootanddiffa 24
┌─┬─┐
│8│4│
└─┴─┘
   rootanddiffa 26
┌─┬─┐
│1│5│
└─┴─┘
   rootanddiffa 99999999999999x
┌──┬────────┐
│_1│10000000│
└──┴────────┘
   rootanddiffb =: 3 : '(y - root ^ 2);(root =. x: <. x: %: y)'
   rootanddiffb 24
┌─┬─┐
│8│4│
└─┴─┘
   rootanddiffb 99999999999999x
┌──┬────────┐
│_1│10000000│
└──┴────────┘