c$++$ The factorial function is important in many fields of mathematics. It is denoted by an exclamation mark following the number to which it is applied.

The factorial function applied to

calculates the product of the numbers from to

$.$

For example, the factorial of

is denoted by $,$ and has a value of

$.$

Two variables fac and n$,$ both of type int, have been declared. n is already initialized with a value, but fac is not.

Write a for loop that calculates the factorial of n and stores the result in fac.