#include <iostream> #include <cmath> using namespace std; double f(double a, double b, double c) { double s = (a + b + c) / 2; return sqrt(s * (s - a) * (s - b) * (s - c)); } int main() { cout.flags(ios::flxed); cout.precision(4); int a, b, c; cin >> a >> b >> c; cout << f(a, b, c) << endl; return 0; }