Write a function called repeater$($s$1,$ s$2,$ n$)$ that given two strings s$1$ and s$2$ and an integer n returns a string that starts with an underscore $(\_),$ then s$1$ and s$2$ alternate n times, then ends with an underscore. $($For those who know loops: you may not use loops to solve this questions.$)$

Testing your code:

Here is what the output of your function should look like when you make the following function calls: