Given an integer, num, return its base seven representation as a string.

LuckySeven.kt

fun convertToBase7(num: Int): String {
    return num.toString(radix = 7)
}

/*
Given an integer num, return a string of its base 7 representation.
Example 1:

Input: num = 100
Output: "202"
Example 2:

Input: num = -7
Output: "-10"

Ex: Given the following num...
num = 42, return “60”.
* */


/*
In a positional numeral system, the radix or base is the number of unique digits, 
including the digit zero, used to represent numbers. For example, 
for the decimal/denary system (the most common system in use today) the radix (base number) is ten, 
because it uses the ten digits from 0 through 9.

Radix is a Latin word for "root". Root can be considered a synonym for base, in the arithmetical sense.
**/