#include <iostream>

//heron: https://en.wikipedia.org/wiki/Heron%27s_formula
//glasi: a=sqrt(s(s-a)(s-b)(s-c))
//operatori: *,/,sqrt 
int main() {
	double s1, s2, s3;
	std::cout << "unesi 3 stranice:";
	std::cin >> s1 >> s2 >> s3;
	std::cout << "povrsina je: " << (s1 + s2 + s3) / 2;

}