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Problems with radial blur

So I am trying to replicate effect shown it this video:https://youtube.com/watch?v=4ccBjlAFt0s
But I am getting errors in lerp node (I added screenshot)

Here is the code:
https://pastebin.com/YWpj4rac

Can you tell me whats wrong?

P. s I am absolute noob, I work with blender but unreal 4 is totally new to me so I probably won’t understand some advanced stuff.
P.s.s I have deadline in 2 days, I would appreciate an answer asap

Thank you

Ok I just accidentally skipped a part where I had to tick one thing in mask to leave only alpha.