How to copy display cell information according to another cell's input?

I'm trying to do the following. Sheet 2 is initially blank until user input in column A. Column B will depends on column Sheet2's column A's input and grab data from Sheet 1 according to what was input into Sheet2's column A's input.

I know there is a way to do if loops many many times but it's not logically to do if conditions for 130 items. Any possibility of shortening this process?

On Sheet 1:
A1 = 1, B1 = Class 1
A2 = 2, B2 = Class 2
A3 = 3, B3 = Class 3
A4 = 4, B4 = Class 4
A5 = 5, B5 = Class 5

On Sheet 2:
A1 = 3, B1 = if(A1=Sheet1!B3,""),
A2 = 1, B2 = if(A2=Sheet1!B1,""),
A3 = 2, B3 = if(A3=Sheet1!B2,""),