# Factstone Benchmark

Factstone Benchmark

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>
int main()
{
int y,i;
double sum;
while(scanf("%d",&y)!=EOF,y)
{
sum=0;
if(y==1960)
printf("3\n");
else
{
for(i=1;;i++)
{
sum+=log10(i)/log10(2);
if(sum>pow(2,(y-1960)/10+2))
break;
}
printf("%d\n",i-1);
}
}
return 0;
}``````

``````#include <iostream>
#include <cmath>
#define MAX 21
using namespace std;
int f[MAX];
int g[MAX];
int main()
{
int i;
f[0]=1<<2;
g[0]=3;
for(i=1;i<MAX;i++)
{
f[i]=f[i-1]<<1;
int m=f[i];
double sum=0;
int base=2;
while(sum+log2(base)<=m)
{
sum+=log2(base);
base++;
}
g[i]=base-1;
}
int n;
while(cin>>n&&n)
{
int t=(n-1960)/10;
cout<<g[t]<<endl;
}
return 0;
}
``````