#include<algorithm>
#include<iostream>
#include<string.h>
#include<stdio.h>
#include<math.h>
using namespace std;
const int INF=0x3f3f3f3f;
const int maxn=100010;
const double PI=acos(-1.0);
const double eps=1e-8;
typedef long long ll;

int main()
{
    double r,hr,hz,vc,vu,d,a,b,hh;

    while(~scanf("%lf%lf%lf",&r,&hr,&hz))
    {
        if(hr<r)
        {
            d=sqrt(r*r-hr*hr);
            if(hz<=d)
                vc=2*PI*hr*hr*hz;
            else
            {
                hh=min(hz,r);
                a=PI*r*r*hh-PI*hh*hh*hh/3;
                b=PI*r*r*d-PI*d*d*d/3;
                vc=2*(PI*hr*hr*d+a-b);
            }
        }
        else
        {
            if(hz<=r)
                vc=2*(PI*r*r*hz-PI*hz*hz*hz/3);
            else
                vc=4*PI*r*r*r/3;
        }
        vu=4*PI*r*r*r/3+PI*hr*hr*hz*2-vc;
        //printf("%lf %lf\n",vc,vu);
        printf("%.6lf\n",vc/vu);
    }
    return 0;
}