sicily 1119. Factstone Benchmark

1119. Factstone Benchmark

Constraints

Time Limit: 1 secs, Memory Limit: 32 MB

Description

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.

Input

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

Output

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

Sample Output

38

题目分析

已知year电脑的位数为bits = pow(2, (year-1960)/10+2)
能表示的最大无符号数为pow(2, bits)
求最大的n使n! <= pow(2, bits)
直接做肯定溢出
将两边取log再做运算

#include <stdio.h>#include <math.h>int main(){  int year;  while (scanf("%d", &year) && year) {    if (year >= 1960 && year <= 2160) {      double bit = pow(2, (year - 1960) / 10 + 2);            double sum = 0;      int count = 2;      while (sum <= bit) {        sum += log(count) / log(2);        count++;      }      printf("%d\n", count - 2);    }  }  return 0;}