10286 - Trouble with a Pentagon

#include<stdio.h>
#include<math.h>
#define f 1.0673956817111818692592637626711
int main()
{
    double b;
    freopen("in.txt","r",stdin);
    while(scanf("%lf",&b)==1)
        printf("%0.10lf\n",f*b);
    return 0;
}