Write a class named duplicate that use a method named duplicateDigits

long duplicateDigits$($long n$)$

that, given a long integer n that is here guaranteed to be positive, returns the integer

constructed by writing its digits twice in a row.

For example, when called with argument $1504,$ this method would return $15041504.$ You

may not convert n to a string at any time, but must calculate the answer using only loops,

conditions and basic integer arithmetic.

Your method must work correctly for all positive values of n less than one million. $($Hint: think

of how you would check whether n consists of one digit, and how you would calculate the

duplicated number in such case. Then think of two digits, three digits, four digits and higher

until you can see and can implement the general pattern.$)$