Factstone Benchmark

Problem B: Factstone BenchmarkDescription

 

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. TheFactstone rating is defined to be the largest integer n such thatn! 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 containingy. A line containing 0 follows the last test case. For each test case, output a line giving the Factstone rating.

Sample Input

196019810

Output for Sample Input

38

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这是一个好题啊，刚开始还以为是个普通的比较题，结果发现数还是大，大到TLE，然后用log来避免指数，TLE依旧，然后发现阶层不需要算出来，只要算的过程中符合条件跳出就可以啦啦。

#include <stdio.h>#include <math.h>int main(){    int bit;    int y = 0;    long long n = 0;    double n1 = 0;    while (scanf ("%d",&y),y)    {        y = y - 1960;        bit = 2;        while (y >= 0)        {            bit *= 2;            y -= 10;        }        n1  = 0;        n = 0;        while (n1 < bit)        {            n++;            n1 += log(n)/log(2);        }        n--;        printf ("%d\n",n);    }    return 0;}