문제

링크

풀이

#include <iostream>
using namespace std;
 
void solve(void) {
  int w, h; cin >> w >> h;
 
  cout << w*h/2 << "." << ((w*h) & 1 ? "5" : "0");
}
 
int main(void) {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
 
  solve();
  return 0;
}