Samsung Note 3 help needed

A

AC Question

So yesterday I went to change my password number on the lock screen.I slept and just now I was unable to unlock as I had forgotten the numbers.

It contains 4 digits and has only 4 and 7 in the code.I want to know how many codes are there with numbers 4 and 7 in a 4 digit code?

I do not want to factory reset my phone.I am willing to take the hard way.