in C .. please the output to be exactly as below.

It is the promotional season and everybody can buy the second item for half price. You will be given the amount bought ( nr. of items) and the unit price of n items. Calculate the total price. Input specification: You will be first given an integer (n), then in the following n lines you will be given two integers. Nr of items: which can be only one or two. Unit price of each item: an int. Output specification: Show one floating point number with two-digits precision: the total price