Imports System
Imports System.Numerics
'
' This program computes the factorial of numbers greater than 20.
' VB.NET provides the BigInteger type, which supports arbitrary‑precision
' arithmetic and is ideal for very large factorials.
'
Module BigFactorial
'
' Compute factorial using BigInteger.
' The algorithm multiplies numbers from 2 to n.
' BigInteger handles overflow internally and grows as needed.
'
Function FactorialBig(n As Integer) As BigInteger
Dim result As BigInteger = BigInteger.One
For i As Integer = 2 To n
result *= i
Next
Return result
End Function
'
' Main entry point: read input, compute factorial, print result.
'
Sub Main()
Console.Write("Enter a number greater than 20: ")
Dim n As Integer = Integer.Parse(Console.ReadLine())
Dim result As BigInteger = FactorialBig(n)
Console.WriteLine()
Console.WriteLine("Factorial of " & n & " is:")
Console.WriteLine()
Console.WriteLine(result)
End Sub
End Module
'
' run:
'
' Enter a number greater than 20: 25
'
' Factorial of 25 is:
'
' 15511210043330985984000000
'
