Maximum of sum and product of digits

Given a number N, the task is to print the maximum between the sum and multiplication of the digits of the given number until the number is reduced to a single digit. Note: Sum and multiplication of digits to be done until the number is reduced to a single digit. Let’s take an example where N = 19, 19 breaks into 1+9=10 then 10 breaks into 1+0=1. 1 is a single digit sum. Also, 19 breaks into 1