#include<stdio.h>

#include<iostream>

#include<algorithm>

#include<math.h>

#include<string.h>

#include<iomanip>

using namespace std;

//const double esp=1e-5;

int main()

{

    double L,n,c,s,r,h;

    while(~scanf("%lf %lf %lf",&L,&n,&c))

    {

        if(L<&&n<&&c<)

            break;

          //

        s=L*(+n*c);

        double low=0.0;

        double high=L*0.5;

        double mid;// printf("%lf\n",s);

        while(high-low>0.00001)

        {

            mid=(high+low)/;

            r=(*mid*mid+L*L)/(*mid);

            if(*r*asin(L/(*r))<s)

              low=mid;

            else

              high=mid;

        }

        h=mid;

        cout<<fixed<<setprecision()<<h<<endl;

      //printf("%.3f\n",mid);

    }

}