HDU 2289 Cup

#include<iostream>
#include<cmath>
#include<cstring>
#include<algorithm>
#include<iomanip>
using namespace std;
#define LL long long
#define pb push_back
#define pi 3.141592653589
#define mem(a,b) memset(a,b,sizeof(a))

const double eps=1e-9;
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int t;
    cin>>t;
    while(t--)
    {
        double r,R,H,V;
        cin>>r>>R>>H>>V;
        double ll=0,rr=H;
        double mid=(ll+rr)/2;
        while(rr-ll>=eps)
        {
            double tr=r+mid*(R-r)/H;
            if((pi*mid)/3*(tr*tr+tr*r+r*r)<V)ll=mid;
            else rr=mid;
            mid=(ll+rr)/2;
        }
        cout<<fixed<<setprecision(6)<<mid<<endl; 
    }
    return 0; 
}