/*
khanhtaon (*︾▽︾)
*/
#include <bits/stdc++.h>
using namespace std;
double ncv, cd, cr, dc, a, b;
int main()
{
    cin >> ncv >> dc;
    ncv /= 2;
    dc = dc * dc;
    a = (ncv + sqrt(2*dc - ncv*ncv))/2;
    b = (ncv - sqrt(2*dc - ncv*ncv))/2;
    cout << a*b;
    return 0;
}

#include<bits/stdc++.h>
#define ll long long
using namespace std;

int main(){
    //( •̀ ω •́ )
    double cv,c,dt,a,b;
    cin>>cv>>c;
    a=(cv/2+sqrt(2*c*c-cv*cv/4))/2;
    b=(cv/2-sqrt(2*c*c-cv*cv/4))/2;
    cout<<a*b;
    return 0;
}