# Lucky Number – Code Fight

So Here is another challenge from the Code Fights, that I solved today. The problem is as following:

Petya loves lucky numbers very much. Everybody knows that lucky numbers are positive integers which decimal representations contain only the lucky digits `4` and `7`. For example, numbers `47`, `744`, `4` are lucky and `5`, `17`, `467` are not.

Petya loves tickets very much. As we know, each ticket has a number that is a positive integer. Its length equals `n`. Petya calls a ticket lucky if the ticket’s number is a lucky number, and the sum of the digits in the first half (the sum of the first `n / 2` digits) equals the sum of digits in the second half (the sum of the last `n / 2` digits). Check if the given ticket is lucky.

Example:

`LuckyTicket(2, "47") = "NO"`

• [input] integer n
• The number of digits. `n` is always even, `2 ≤ n ≤ 50`
• [input] string s
• The number of the ticket.
• [output] string
• `"YES"` if the given number is lucky, `"NO"` otherwise.

The solution to the above problem is as following:

**NOTE: I have used ‘//’ instead of simple ‘/’ is because in Python 3 if you use ‘/’ to divide a number it will return a float instead of integer. In order to force the compiler to return an integer during a division we need to use ‘//’. Hope this helps.

Credit for the creation of Problem: Code Fights 