1119. Factstone Benchmark

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. 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.

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 containing y. A line containing 0 follows the last test case. For each test case, output a line giving the Factstone rating.

Sample Input

1960
1981
0

Sample Output

3
8

// 对两个数同时去对数然后再进行比较,避免数字过大带来的超时
// 与n的阶乘进行比较
#include
#include
using namespace std;

int main() {
  int year;
  while (cin >> year && year) {
    int bit;
    int r = (year - 1940)/10;
    bit = pow(2, r);
    double loguint = bit*log(2); //  取对数, 无符号数的位数
    double res = 0;
    int i;
    for (i = 1; i < 10000000000; ++i) {
      res += log(i);
      if (res > loguint) break;
    }
    cout << i - 1 << endl;
  }
  return 0;
}