Given two numbers as stings s1 and s2 your task is to multiply them.

Example 1:

Input:
s1 = 33
s2 = 2
Output: 66

Example 2:

Input:
s1 = 11
s2 = 23
Output: 253

Your Task:

You are required to complete the function multiplyStrings() which takes two strings s1 and s2 as its only argument and returns their product as strings.

Expected time complexity: O( n₁ * n₂ )
Expected auxiliary space: O( n₁ + n₂ ) ; where n₁ and n₂ are sizes of strings s1 and s2 respectively.

Constraints:
1 <= length of s1 and s2 <= 10³

Note:The Input/Ouput format and Example given are used for system's internal purpose, and should be used by a user for Expected Output only. As it is a function problem, hence a user should not read any input from stdin/console. The task is to complete the function specified, and not to write the full code.