Caesar Cipher

Problem Background

Special for beginners, ^_^

Problem Description

Julius Caesar was very clever and came up with a simple and effective encryption system: given any lowercase English letter $\,x$, just take the 3rd letter after it as its encrypted letter; the last 3 letters map cyclically back to the first 3 letters.

The encryption scheme is as follows:

$a\rightarrow d,\,b\rightarrow e,\,c\rightarrow f,\,\cdots,\,x\rightarrow a,\,y\rightarrow b,\,z\rightarrow c$

Now you are given a character $\,c$; please give its encrypted letter!

Input Format

One lowercase English letter.

Output Format

One lowercase English letter: the encrypted letter.

Sample Input 1

a

Sample Output 1

d

Sample Input 2

x

Sample Output 2

a

Constraints

1s, 1024KiB for each test case.

Hint

• Letters can be added to or subtracted from integers: c + 3 just counts three letters forward.
• The trouble is that x, y, z go past 'z' — think about how to wrap them back around to 'a'. Modular arithmetic may help (first turning the letter into a 0–25 index makes things easier).
• Check against the samples: a → d; x → a.