Extra Long Factorials

The factorial of the integer n, written n!, is defined as:

n! = n x (n - 1) x (n - 2) x … x 3 x 2 x 1

Calculate and print the factorial of a given integer.

For example, if n = 3, we calculate 30 x 29 x 28 x … x 3 x 2 x 1 and get 265252859812191058636308480000000.

Function Description

Complete the extraLongFactorials function in the editor below. It should print the result and return.

extraLongFactorials has the following parameter(s):

• n: an integer

Note: Factorials of n > 20 can’t be stored even in a 64-bit long long variable. Big integers must be used for such calculations. Languages like Java, Python, Ruby etc. can handle big integers, but we need to write additional code in C/C++ to handle huge values.

We recommend solving this challenge using BigIntegers.

Input Format

Input consists of a single integer n

Constraints

• 1 <= n <= 100

Output Format

Print the factorial of n.

Sample Input

1

25

Sample Output

1

15511210043330985984000000

Explanation

25! = 25 x 24 x 23 x … x 3 x 2 x 1

Solution

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// Complete the extraLongFactorials function below.
function extraLongFactorials(n) {
    let memoization = [BigInt(0), BigInt(1)];

    const factorial = num => (typeof memoization[num] !== 'number')
        ? ((num - BigInt(1)) > 0
            ? (num * factorial(num - BigInt(1)))
            : BigInt(1)
        )
        : memoization[num]

    console.log(String(factorial(BigInt(n))));
}