Question: ```py
package = input("Enter a package designation A,B, C: ")

while package != 'a' or package != 'A' or package != 'b' or package != 'B' or package != 'c' or package != 'C':
    print("Erorr:you didn't enter a valid package")
    package = input("Enter a package designation A,B, C: ")

```

Every time I input the letters a-c or A-C the compiler gets stuck in the while loop even though I continue to re-enter the values and the code say's this as long as the package doesn't equal these values

Answer: 
Well there a pretty good reason for this.

Let me explain this below so I can make it easy for you.(I hope)

Every time you are giving a letter the condition will be True.
But why is that?

**Let's debug this together:**
`package = input("Enter a package designation A,B, C: ")`

We are giving for an example the letter `"c"`

`package <== "c"`

**And then we are checking the condition for the while loop:**

`package != 'a' or package != 'A' ==> True`

`package != 'b' or package != 'B' ==> True`

`package != 'c' or package != 'C' ==> True` But wait.. how is that even possible?

Well `package != "c" ==> False` but `package != 'C' ==> True`

So what's the condition's outcome? **True**

That's because the or statement returns **True** if one of the conditions is **True**.

That's the reason you are stuck in an endless loop.

**The Solution:**

```
package = input("Enter a package designation A,B, C: ")
letters = "abcABC"

while package not in letters:
    print("Erorr:you didn't enter a valid package")
    package = input("Enter a package designation A,B, C: ")

```

You should know that there are better solutions to this problem but i wanted to go for a simplier approach.

Anyway hope that helps.
The condition is always `True` due to the `or`s.
Putting all the conditions into one simple conditional statement solves this.

```
package = str(input("Enter a package designation A,B, C: "))
while package.lower() not in ['a','b','c']:
    print("Erorr:you didn't enter a valid package")
    package = str(input("Enter a package designation A,B, C: "))

```