Goal: Learn to replace characters in strings.

Assignment: A Caesar cipher is a method to encrypt messages by which each character in the message is shifted by a certain amount, to the left or to the right, in the alphabet. The amount by which the characters are shifted is known as the key. For example, the letter $"$A$"$ with a key of three to the right would be encrypted as $"$D$".$

On its own, a Caesar cipher is pretty easy to break. However, it still has applications today $($e$.$g$.,$ ROT$13).$

Write a program that reads a string of text as input, applies the Caesar cipher to said text, and displays the encrypted message to the user.

In your program, the built$-$in functions ord and chr will be helpful. The ord function takes a character as its argument and returns an integer code representing that character. For example,

the expression ord$(\text{'}$A$\text{'})$ returns $65$

the expression ord$(\text{'}$B$\text{'})$ returns $66$

the expression ord$(\text{'}$C$\text{'})$ returns $67$

and so forth.

The chr function takes an integer code as its argument and returns the character that code represents. For example,

The expression chr$(65)$ returns $\text{'}$A$\text{'}$

The expression chr$(66)$ returns $\text{'}$B$\text{'}$

The expression chr$(67)$ returns $\text{'}$C$\text{'}$

and so forth.

Also, assume a variable named key containing the cipher's integer key has already been assigned. A negative key means the characters are shifted left, and a positive key means the characters are shifted right.

Note: Do not display a prompt for the user, just use input$().$

Sample Run $($User input enclosed in $<>)$

iboet!pgg$!$nz$!$nbdbspoj