finding or matching data

Ok so this has been bugging me for a week or so and i have attempted many functions to no avail.

My spreadsheet consists of two columns, column A holds a series of numbers whilst column B, again holds a series of numbers but with an added single letter on the end.

What I would like to do is find a function which will match the numbers and letter in column B with the corresponding numbers in column A and then place the result in column C. eg

A B C
9111111 1234567H 9111111B
6789109 4567888
1234567 9111111B 1234567H

Hope that make sense anyway.

Any help on that would be great as I am not the greatest at functions.

James