You are given two non$-$empty lists representing two non$-$negative integers. The digits are stored in reverse order, and each element in the lists contains a single digit. Write a programme that adds the two numbers and return the sum as a list. You may assume the two numbers do not contain any leading zero, except the number $0$ itself. For example, for an input of l$1=[2,4,3]$ and l$2=[5,6,4],$ the output is $[7,0,8]$ because $342+464=807.$