#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>

using namespace std;

int main()
{
  int a, b, c;
  cin >> a >> b >> c;
  double s = (a + b + c) / 2;
  double ans = 2.0 * sqrt(s) / (a + b + c) * sqrt(s - a) * sqrt(s - b) * sqrt(s - c);
  printf("%.10f\n", ans);
}