#include <cmath>
#include <cstdio>
#include <iostream>
#include <algorithm>

using namespace std;

const double PI = acos (-1.0);

double r, hr, hz;

double fun (double x){
    return PI*(r*r*x - 1.0/3.0*x*x*x);
}

double jj (double x, double y){
    return fun (y) - fun (x);
}

int main (){
    int xx, yy, zz;
    while (~scanf ("%d%d%d", &xx, &yy, &zz)){
        r = xx, hr = yy, hz = zz;
        double VC = 0.0, VU = 0.0;
        if (hr <= r){
            double h = sqrt (r*r - hr*hr);
            if (hz <= h){
                VC = PI * hr * hr * hz * 2.0;
                VU = 4.0/3.0 * PI * r*r*r;
            }else{
                VC = PI * hr * hr * h * 2.0 + jj (h, min (hz, r))*2;
                VU = PI * hr * hr * hz * 2.0;
                if (hz <= r){
                    VU += jj (hz, r)*2.0;
                }
                VU += jj (0, h)*2.0 - PI * hr * hr * h*2.0;
            }
        }else{
            if (hz >= r){
                VU = PI * hr * hr * hz * 2.0;
                VC = 4.0/3.0 * PI * r*r*r;
            }else{
                VC = jj (0, hz) * 2;
                VU = PI * hr * hr *hz * 2.0 + jj (hz, r)*2.0;
            }
        }
        printf ("%.6f\n", VC/VU);
    }
}