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`

- The number of digits.
**[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