#include <bits/stdc++.h>
int main() {
  unsigned long long H, W;
  std::cin >> H >> W;
  double lc1 = W / 2 + W % 2;
  double lc2 = W / 2;
  double tc1 = lc1 * (H / 2 + H % 2);
  double tc2 = lc2 * (H / 2);
  std::cout << tc1 + tc2;
  return 0;
}
