2000.py

#!/usr/bin/env python 
# Author: kangkang <[email protected]> 2011 
# Licence: GPLv3 

import sys 
class Res(): 
    def __init__(self): 
        self.result = [] 

    def add(self, value, offset): 
        if len(self.result) < (len(str(value))+offset): 
            zfill = len(str(value))+offset - len(self.result) 
            for i in range(zfill): 
                self.result.append(0) 
        for i in range(len(str(value))): 
            r = int(str(value)[::-1][i])+self.result[i+offset] 
            self.result[i+offset] = r%10 
            if r >= 10: 
                self.add(1,offset+i+1) 

    def get(self): 
        return self.result 


if __name__ == "__main__": 
    n=int(sys.argv[1]) 
    res = Res() 
    res.add(1,0) 
    for i in range(n)[1:]: 
        t = [] 
        for offset in range(len(res.get())): 
            t.append((res.get()[offset]*i, offset)) 
        for k,o in t: 
            res.add(k,o) 

    result = [str(x) for x in res.get()] 
    result.reverse() 
    r = int(''.join(result)) 

    print(r)