C++ :

#include<iostream>
using namespace std;
int b,c,a[10000],i,j,pd;
int main()
{
    cin>>b;a[0]=1;pd=0;c=0;
    for (j=1;j<=b;j++)
    {
        for (i=0;i<=pd;i++)
        {
            a[i]=a[i]*j+c;
            c=a[i]/10;
            a[i]=a[i]%10;
        }
        if (c!=0) 
        {
            pd++;a[pd]+=c;
            while (a[pd]>9) pd++,a[pd]+=a[pd-1]/10,a[pd-1]=a[pd-1]%10;
        }
        c=0;
    }
    for (j=pd;j>=0;j--) cout<<a[j];
    //system("pause");
    return 0;
}

Pascal :

var s,ss:string;
    i,n:longint;

procedure gjd(s1,s2:string);
var a,b,c:array[1..256] of longint;
    ss,sss:string;
    la,lb,lc,i,j,t:longint;
begin
  fillchar(a,sizeof(a),0);
  fillchar(b,sizeof(b),0);
  fillchar(c,sizeof(c),0);
  la:=length(s1); lb:=length(s2);
  for i:=1 to la do
    a[la-i+1]:=ord(s1[i])-ord('0');
  for i:=1 to lb do
    b[lb-i+1]:=ord(s2[i])-ord('0');
  for i:=1 to la do
  begin
    t:=0;
    for j:=1 to lb do
    begin
      c[i+j-1]:=c[i+j-1]+a[i]*b[j]+t;
      t:=c[i+j-1] div 10;
      c[i+j-1]:=c[i+j-1] mod 10;
    end;
    c[i+j]:=t;
  end;
  lc:=la+lb;
  while (c[lc]=0) and (lc>1) do dec(lc);
  ss:=''; sss:='';
  for i:=lc downto 1 do
  begin
    str(c[i],ss);
    sss:=sss+ss;
    ss:='';
  end;
  s:=sss;
end;

begin
  readln(n);
  s:='1';
  for i:=2 to n do
  begin
    str(i,ss);
    gjd(s,ss);
  end;
  writeln(s);
end.

Java :

import java.math.BigInteger;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner cin=new Scanner(System.in);
		int n=cin.nextInt();
		BigInteger s=BigInteger.valueOf(1);
		for (int i=1;i<=n;i++)
		{
			s=s.multiply(BigInteger.valueOf(i));
		}
		System.out.println(s);
	}
}

Python :

# coding=utf-8
s=1
n=eval(input())
for i in range(1,n+1):
    s*=i
print(s)