# include <iostream>
using namespace std;
int main()
{
     float masahat, ghaede, ertefa;
     cout << "ertefae mosallas ra vared konid: ";
     cin >> ertefa;
     cout << "ghaedeye mosallas ra vared konid: ";
     cin >> ghaede;
     masahat=ertefa*ghaede/2;
     cout << "masahate mosallas: " << masahat << endl;
}