#include
#include
int main()
{
double m,p,d,r;
scanf("%lf%lf%lf",&p,&d,&r);
m=(log(p)-log(p-d*r))/log(1+r);
printf("%.2lf\n",m);
return 0;
}
#include
#include
int main()
{
double m,p,d,r;
scanf("%lf%lf%lf",&p,&d,&r);
m=(log(p)-log(p-d*r))/log(1+r);
printf("%.2lf\n",m);
return 0;
}