Excel formula to match first 3 digits in 2 columns

I have 2 columns of numbers in Excel. I want to match first 3 digits of column A with the first 3 numbers of column B and if they are the same, in column C I need to fill in the data same if not then not same. I have a list of 16 thousand entries in Excel and need a quick way to figure this out.

eg.

A1: 810123 B1: 810567 then column c should say "same" because the first 3 numbers match.A2: 801123 B2: 803123 then column c should say "notsame" because the first 3 numbers do not match.

Thank you for your help.