Add Strings

You are given two non-negative integers represented as strings. Your task is to add the two numbers and return the sum as a string.

The addition should be performed digit by digit from right to left (i.e., from the least significant digit to the most significant digit), handling any carry that results from the addition.

In other words, you need to simulate the standard addition algorithm taught in school. Use the formula \(carry = \lfloor \frac{n_1 + n_2 + carry}{10} \rfloor\) and \(digit = (n_1 + n_2 + carry) \mod 10\).

inputFormat

The input consists of two lines. The first line contains the first non-negative integer as a string, and the second line contains the second non-negative integer as a string. You may assume that the numbers do not contain any leading zeros except for zero itself.

outputFormat

Output the sum of the two numbers as a string.

123
456

579