Index trhough multiple columns and return value

Hi all

i have two sheets (sheet1 & sheet2) with 2 columns each; one for staff code and other for account number.

In the third sheet i.e. Summary sheet, i have all the staff codes in the first row. Now, i need their account number to display against the respective staff code. I tried index and match, vlookup but to no avail.

Help me

attaching file for quick understanding.