#include <iostream>
#include <math.h>

using namespace std;

char s[4];

void print (int a)
{
    int i(3), b = a;
    while (i+2) s[i--] = (char)(b%10 + '0'), b/=10; 
    cout << a/10000 << '.' << s << "\n";
}

int main ()
{
    double p, q, r;
    cin >> p >> q >> r;
    if (p != r)
      {
        cout << "0\n";
        cin >> p;
        return 0;
      }
    print(ceil(2*(p*(p+q)*10000)));
cin >> p;
}
