How to compare two columns and show the value in another column in SQL Server

I have two columns

col1           col2       Result

12 34        12         34

54 76        76         54

13 55       13 55      Same

Need to compare two columns and return the value as shown above. For example in first tuple in col1 there 12 and 34 and in col2 there is only 12 so in result column it should display 34, because 34 is missing in col2