Im a programer for quite sometime now.. and I really need help with my next assignment, I need to.. Wait for it.. make a program that gets numbers and traslates it to letters with a secret principle that only I should know.
the numbers are aligned not at all randomly and it's basicly a "code language" to communicate privatly.

So in short, my question is how can I tell a program in C++, to see lots of numbers, know the principle and translate it to letters and words.
I'll give an example:

1431341541541234 = Hello