#include <bits/stdc++.h>

using namespace std;

void fast_io() {
	ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
}

int main() {
	fast_io();
	using ld = long double;
	long long a, b, c;
	cin >> a >> b >> c;
	ld theta = acos((a * a + b * b - c * c) / (2.0 * a * b));
	ld area = 0.5 * a * b * sin(theta);
	ld s = (a + b + c) / 2.0;
	ld r = area / s;
	cout << setprecision(16) << fixed << r << endl;
}