You're trying to come up with a good Codeforces username. You want to use something similar to your real name, but not exactly your real name, to not release too much info about yourself online. Thus, you decide to encode your username using an Affine cipher.

An affine cipher uses a key of two values: $$$a$$$ and $$$b$$$. Given a letter $$$l$$$, you first convert it into it's "character code", for example, "a" would become $$$0$$$, "b" would become $$$1$$$, etc. We'll call this $$$x$$$. Then, you calculate the value of $$$a$$$$$$x$$$ + $$$b$$$ mod $$$26$$$, and reverse the character code mapping that you used previously, to convert the answer back into a letter. The affine cipher runs this process on all letters (not spaces) in a given string.

For example, let's use the letter $$$c$$$, and a key of $$$a$$$ = $$$15$$$, and $$$b$$$ = $$$5$$$. $$$c$$$ has a character code of $$$2$$$. Then, the encoded character has a character code of $$$15$$$*$$$2$$$ + $$$5$$$ mod $$$26$$$ = $$$35$$$ mod $$$26$$$ = $$$9$$$. Thus, the encoded character is $$$j$$$.