using System;

namespace BigFactorial

$\{$

class Program

$\{$

static void Main$($string$[]$ args$)$

$\{$

Console.WriteLine$("$Enter a number to compute its factorial:"$)$;

int n $=$ int.Parse$($Console$.$ReadLine$())$;

int$[]$ factorial $=$ new int$[5001]$;

factorial$[0]=1$;

int length $=1$;

while $($n $>=0)$

$\{$

length $=$ ComputeFactorial$($n$,$ factorial$)$;

Console.WriteLine$("$The factorial of $"+$ n $+"$ is:$")$;

Console.WriteLine$("$Number of digits: $"+$ length$)$;

DisplayFactorial$($factorial$,$ length$)$;

Console.WriteLine$("$

Enter a number to compute its factorial $($negative to exit$)$:$")$;

n $=$ int.Parse$($Console$.$ReadLine$())$;

$\}$

$\}$

static int ComputeFactorial$($int n$,$ int$[]$ factorial$)$

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int carry $=0$;

for $($int i $=0$; i $<$ factorial.Length; i$++)$

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factorial$[$i$]=$ factorial$[$i$]*$ n $+$ carry;

carry $=$ factorial$[$i$]/1000000$;

factorial$[$i$]\%=1000000$;

if $($factorial$[$i$]>0$ && carry $==0)$ break;

$\}$

int length $=$ factorial.Length;

while $($length $>1$ && factorial$[$length $-1]==0)$

length$--$;

return length;

$\}$

static void DisplayFactorial$($int$[]$ factorial, int length$)$

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Console.Write$($factorial$[$length $-1])$;

for $($int i $=$ length $-2$; i $>=0$; i$--)$

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Console.Write$($String$.$Format$("\{0$:$000000\}",$ factorial$[$i$]))$;

$\}$

$\}$

$\}$

$\}$