Don't know how to do that.

Good evening, I have been asked to do a program that takes a series of numbers and that makes this a palindrome series (readable from left to right or from right to left without changing anything). An example that was made to me is to enter 5 values from the keyboard, for example, 12345, and to be able to write this series as 12321. The language is C. Thanks to everyone and good evening again