Check the King!

This is a game where you post a puzzle and you have to find the fastest way to check(or checkmate) the opponents King! Rules:

The only piece that can move is the rook.(The opponents king is the only piece that they can move.)

You cannot endanger the rook.

The King cannot endanger the rook(so if the king can move up or down and it endangers the rook your game is wrong.)

The opponents King can only move up or down.

You cannot make the opponents king unable to move anywhere up or down.

The opponent only can move the king.

there can only be ONE ANSWER!

EXAMPLE:

4n3/1p5k/5pp1/p1n4p/8/3n3p/4b3/R7 w - - 0 1

I can't post a chess position with my phone but this is the code of the position I created

oops sorry about 2nd move!

I have one but I don't know how to create and post it.

I tried with "Insert chess game or diagram" but I don't know how to make a puzzle.  Can anyone explain me how to do it?

do you use android IOS,or computer?

Computer

First: click on the mini board on top left

Then click "set up position"

Then set up your starting position

Then click on "Moves"

Then drag your pieces where you want them to go.

Then(optional) click on details and do your details

After click on "theme" and there should be a box that says"puzzle" and click on box. You can also flip the board.

Finally click insert then post!

good job