Amtel has announced that it will release a 128-bit computer chip by 2010, a 256-bit computer by 2020, and so on, continuing its strategy of doubling the word-size every ten years. (Amtel released a 64-bit computer in 2000, a 32-bit computer in 1990, a 16-bit computer in 1980, an 8-bit computer in 1970, and a 4-bit computer, its first, in 1960.)
Amtel will use a new benchmark - the Factstone - to advertise the vastly improved capacity of its new chips. The Factstone rating is defined to be the largest integer n such that n! can be represented as an unsigned integer in a computer word.

Given a year 1960 ≤ y ≤ 2160, what will be the Factstone rating of Amtel‘s most recently released chip?

There are several test cases. For each test case, there is one line of input containing y. A line containing 0 follows the last test case. For each test case, output a line giving the Factstone rating.

1960
1981
0

3
8

#include <stdio.h>
#include <math.h>
#define MAX 210
#define PI 3.14159265358979323846
#define E 2.7182818284590452354
int main()
{
	int ans[MAX] ;
	int j = 1 ;
	for(int i = 0; i < MAX ; ++i)
	{
		for( ; ; ++j)
		{
			if(0.5*log10(2*PI*j)+j*log10(j/E)>pow(2.0,i/10+2)*log10(2.0))
			{
				ans[i] = j-1 ;
				break ;
			}
		}
	}
	int year ;
	while(~scanf("%d",&year) && year)
	{
		printf("%d\n",ans[year-1960]);
	}
	return 0 ;
}