case sensitivity

this problem is driving me insaaaaane!!!!
even though i bet the answer is simple.
using if else i have to:

Write a C++ program that first determines whether an entered character is an upper case letter.
If the letter is uppercase, determine and print its position in the alphabet.
Hint- If the entered character is upper case, its position can be determined by
subtracting 'A' from the letter and adding 1.

brain not functioning, please help >_