mouse click provided that the speed is zero

I’m a newbie! Greetings to all developers at UE4, we are one team.
Immediately I ran into the problem of which node to use to set the variable fight to 1 when the left mouse button was pressed. I use player controler and is input key down, but I don’t know how to check if the speed is 0. I would be grateful for any help!

The speed of what?