Write a function factorial() that takes a positive integer as a parameter and returns the factorial of that integer. The main function takes an integer n<=7, as input, and utilizes the factorial function to calculate the following series.

The solution code is written in C++:

Explanation:

Firstly, create a function factorial with one input parameter (Line 1).

Next, create an if-else statement to check if input n is 1, just return the end (Line 6-7).

Otherwise, the function should return n multiplied by output of the recursive calling of the function itself (Line 8-9).

In the main program, create variable and prompt user to input number (Line 15 -17).

Next, do the input validation checking to ensure the input n must be equal or less than 7 then only call factorial function to calculate the factorial of n and display the answer (Line 19 - 20). Otherwise, the program shall just display error message.

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