#include <iostream>


using namespace std;

float bi(float n, float m, float k)
{
    float bis = (sqrt(n * m) * (n + m + k) * (n + m - k)) / (n + m);
    return bis;
}


int main()
{
    setlocale(LC_ALL, "RUS");
    cout << "¢夨򥠤먭 ⠸赠񲮰��砯𮡥렢";
    float a, b, c;
    cin >> a >> b >> c;
    cout << "Ѱ夭奠న��跥񪮥 䫨�豱媲𨱠򰥳㮫�࠰ࢭ " << ((bi(a, b, c) + bi(b, c, a) + bi(c, a, b)) / 3) << endl;
    system("pause");
    return 0;
}