The task is to generate the correct answer for a given math problem.

Input: Consider Input: Problem: a man whose speed is 4.5 kmph in still water rows to a certain upstream point and back to the starting point in a river which flows at 1.5 kmph , find his average speed for the total journey ?

Output: 4


Input: Consider Input: Problem: if a - b = 5 and a 2 + b 2 = 31 , find the value of ab .

Output: 3


Input: Consider Input: Problem: if the price of an article went up by 30 % , then by what percent should it be brought down to bring it back to its original price ?


Output: 23 1 / 13 %