In mathematics, the notation n! represents the factorial of the nonnegative integer n. The factorial of n is the product of all the nonnegative integers from 1 to n. For example,
7!=1×2×3×4×5×6×7=5,040 and
4!=1×2×3×4=24
Write a program that asks the user to enter a positive number. If the user enters a negative the input validation loop should re-prompt the user for a positive number. Then the program uses another loop to calculate the factorial of that number. Note that 0! and 1! are 1. Display the factorial. Your program should continue to re-prompt the user for another number and display the factorial until the user enters a sentinel.