Write a recursive function, `sum(arr, n)`

, that returns the sum of the first `n`

elements of an array `arr`

.

function sum(arr, n) {

// Only change code below this line

if (n <= 1) {

return 0;

} else {

return sum(arr, n - 1) + arr[n - 1];

}

// Only change code above this line

}