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

#include <atcoder/all>
using namespace atcoder;

using ll = long long;
using mint = modint998244353;

int main() {
  long double a ,b, c;
  cin >> a >> b >> c;
  long double s = (a + b + c) / 2.0;
  long double area = sqrt(s * (s - a) * (s - b) * (s - c));
  cout << fixed << setprecision(10) << area / s << endl;
}